So I sent a random shiny Minior.
Mew event said it only gave 500.
Shiny minior costs 1000 DP.
So now I only have 520 points in mew event (I sent a 20DP one
before).
I believe it was because when you sent 1000 dp, it split 500 for
one mew plushie that was sent to your gift log. The rest was added
to the next mew plush