Yikes! That is way too low on AT2 meter, glad he came up for you with just some LC.
2.8=50 on US mg/dL, most members here follow that measurement, so perhaps going forward if you don't mind putting those numbers instead in your title. I understand the mmol/L because I'm in Canada
Your SS says 3.2 but either way, that's still too low on AT2.
The +3 was quite a bit lower than your preshot, so that signalled you would have an active cycle. It might have been worth getting a test at +4 to see what he was up to, and try and slow the drop with some higher carb food.
Regardless of which dosing method you'd like to follow, that 50 (or 57?) earns a reduction down to 13u, but it might be worth re-reading them if you haven't already, since there are also differences in how long to hold doses, in addition to when to take a reduction.
Dosing Methods
Just another observation, when you get a number under 68 on AT2 that would warrant closer monitoring and I would suggest for next time not waiting an hour, but retesting between 20-30 minutes, since you don't want them lingering under 68. It is also suggested you intervene with a teaspoon or two of HC, depending on how carb sensitive your cat is. This time LC seemed ok, but something to consider if (when) you have low numbers again. Here is the info post on
How to Handle Low Numbers
While the references are for human meters, the idea of intervening with HC and testing more frequently remains the same.