This graph shows which bucket of receipt dates USCIS has started processing. You can probably infer which receipt dates are going to be processed next using this graph.
If you seeing a lot (~30-50%+) of green in a portion of the dates e.g. the first half of March then you can safely assume that these dates are actively being processed right now.
If there is only a little green (~10-15%), then one could probably assume that USCIS has started processing these dates too. Sometimes it might look counter intuitive, as in, huge gaps in dates between two areas of green e.g. if 1-Mar to 15-Mar is 30%+ green but 16-Mar to 30-Mar has no green, and then 1-Apr to 15-Apr is 10% green. In this case I would suggest that you either look at how the graphs evolve over time (check them everyday), or look that the "Recent Approvals" graphs to see which dates USCIS is processing these days.
If there is no green in your dates of interest, then it probably means that you are going to have to wait a few days because USCIS has not started processing these cases.
Overall it seems that there is (atleast) some sort of sequence in the order in which the dates are being processed, so I think that it is reasonable to take insight from receipt dates that are 1-2 weeks earlier than your dates of interest.
P.S.This graph is horizonatally scrollable and zoomable.
This graph accompanies the first graph. If you hover over the bars you will see a sorted list of receipt dates.
Things of interest are the sizes of the stacks and the trend over time. From my experience (might not apply everytime) each bar (usually) has 1-4 big stacks in the middle, these represent the group of dates currently being processed.
The stacks at the bottom are older cases (like maybe 6-7 months old). I think that these are special cases (corner cases) that took too much time to process and can be safely ignored.
The stacks at the very top are the latest receipt dates which are being approved right now. I am hoping that these dates will eventually (perhaps in the coming week(s)) become the big stacks in the middle.
This graph shows the number of cases added today, yesterday, and the day before..... This is to help you get a better idea of the current processing speed of USCIS lockboxes.
OPT Timeline's script is run every few hours. Sometimes you might even see cases added a day late.
This graph is against the Approval Date as opposed to the receipt dates. This is to help you anticipate the wait time from OPT approval/card production order till the actual time USPS gets the card. After that you should just be able to use the USPS tracking number provided by USCIS.
If you look at the earliest bar with all yellow, it will most likely be the next one in the sequence to start shipping out.
Looking at the bars that are partially green, we can also see that earlier approvals dont necessarily mean that the card will be shipped earlier, newer dates are being mailed out while older dates are still pending. It looks like there is a range of dates that are being shipped at any time.
P.S. June 24 onwards should be accurate.
This graph is also against approval dates. The X-axis is the last 10 days. The bars show which approval dates had the most cards shipped recently. It will also show you the range of OPT approval dates actively being shipped out right now.
P.S. Jul 6 onwards should be accurate. This is because I implemented this feature quite late and I am only able to retrieve exact shipment dates from now on.
After looking at the trend in the first graph for receipt dates, we see a similar but more pronounced trend, of decreasing (green) approvals with an increase of X-axis, here too. We can see that the earlier receipt dates have more approvals and then the green/number of OPT approvals quickly wanes away into nothing.
This similarity in trend also shows that perhaps there is some link between receipt dates and receipt numbers too.
This graph is also horizonatally scrollable and zoomable.
P.S. Some older receipt numbers are missing here, which is why you see that bar heights increase suddenly near YSC1990180000.