"U2" countries have a high number of entries in the lottery. Therefore, they are more frequently chosen (at random) than entrants from other European countries and at some point they are simply limited, i.e. if chosen the assigned case number is dismissed/concealed ("hole") and the "selectee" gets a not-selected message. So, usually U2 selectees have low case numbers. If the case in question were a U2 case, I would conclude that they messed up the selection and have way too many U2 selectees, which could result in a lower cut-off in September (country limit).
This scenario applies basically only to Uzbekistan. Ukraine has such a high refusal rate, due to fraudulent applications, that it can't possibly hit a country limit, even with, say, 10,000 selectees. Still, I always treat both separately. The rest of Europe is harmless. In AF it's (at least) Egypt, Ethiopia and Ghana, in AS Nepal and Iran. There are no special countries in SA, OC or NA (regional quota below 2,000).
The above mentioned scenario seems currently to play out in DV-2017. Reported Egyptian cases as high as AF42### are not compatible with the 3,850 country limit. "They", whoever that is, realized that AF region had too few selectees to use up the regional quota and decided to drop the limit for Egypt (at c. 32,000 in May), thereby increasing its selectees by an estimated 25-35% – which is completely crazy. They should have raised the number slightly, but massively for non-limited AF countries. Egypt will face a hurting September cut-off.
Lastly, to state for once the obvious: The last paragraph is my opinion only. Others will disagree (and are, hopefully, right).
The estimates are based on what information we have, which is in part circumstantial (reported Egyptian cases).