The bonus only does on BASE RP though, minus any boosters or whatever.
Also, your total was 8,463 looks like to me… not 5,897.
Looks like you got roughly 3,000 base amount, then skill bonus 100% more of that so 3,000. THEN your premium time kicks in only on the base amount, not the skill reward, so another roughly 3,000, for roughly 9,000 total.
Oh right yeah i forgot it was kills only. That definitely explains the few % it was off versus my explanation. Almost all of her reward was from kills, so it’s very close to what you would expect otherwise, but a bit less because kills weren’t quiiiite all of it.
The overall way the numbers are shown in the tabulation screen is just complete confusing garbage though, even though I think it looks like it is calculating correctly. Writing a subtotal as “Total” and mixing raw numbers and multipliers haphazardly, and just generally a complete mess.