Edit: The site is pretty cool. I get strong vibes of the Winfall lottery story[0]
[0] https://highline.huffingtonpost.com/articles/en/lotto-winner...
If 25% of the prizes greater than $30 have been claimed, then I assume 25% of the prizes lesser than $30 have been claimed. Everything in the low numbers has large enough data pools for it to average out accurately. It's not until you get to the $600+ prize level where things would be really inaccurate.
You'll also note there's usually a lag for prizes $600+.
When you look at aggregates across states, you might see something like 25% of prizes below $600 have been claimed but only 19% of prizes above $600 have been claimed. I figure that's because $600+ has to be claimed at lottery headquarters and go on taxes. So people might delay, try to hide the money from their spouse, wait for tax reasons, the headquarters has to manually process it rather than the automated machine at a retail outlet, whatever...
Specifically in `num_tx_initial` it might be because they don't report the number of tickets printed. But if they print the odds of a win and numbers of winners available, then you can estimate how many non-winners there are and thus how many printed tickets there are.