Great question!
The blackout sections are for added rows that didnt exist yet, for example I added github stats in March, and ZH Brazil in Sept, but stopped due to that account getting banned on X in Nov. Can see we also added zechub wiki stats starting in Feb 24ā.
Great question!
The way twitter measures impressions is a bit of a mystery to me because it seems to change. I do know last month we had ATH of impressions so I figured it would be lower this month. This is exactly why I wanted to post the same measurement overtime so the community can get a better visual of performance over the long term.
On the flip-side, if you can suggest a better metric to track, Iām open to ideas.
lol. It does look redacted, though 
Ok so Engagement is up 13% over 28days. Impressions is down nearly 30% - this may be because we posted less.
Engagement = people interacting with posts/viewing profile/following
Impressions = post view count
i can confirm impressions is lower for my acc also in may than april, but april was super active month in twitter for most.
maybe would be good idea to add how many posts were done per month if possible, because that is the thing that affects it most i guess.