The number of officers per day is the left axis, it peaked at 32 on March 6. The right axis, and white line, is tracking the number of troops "eliminated" by the AFU (their definition has never been clarified AFAIK, but it's widely understood not to include wounded).

As for the data, you can download/export the data presented in the visualization by hovering above the graph and 3 dots will appear on the top-right corner. You can export that data from there.

If you want my own data, this is the spreadsheet I keep: https://docs.google.com/spreadsheets/d/1JSPEJpjMMTyAh5NaEVbRB_GEXgrjAFjFpeN3_myLKTc/edit#gid=1132162938

If you want the full breakdown of officer ranks, Twitter user @KilledInUkraine and team is the authority on the subject: https://docs.google.com/spreadsheets/d/1_bpIqkzD88hlSpA-PDZenSQGNnVnxz3lwYHKViSyuUc/edit#gid=1361265165