Looking at the last set of PGN files I received, at the beginning is a new tag followed by lots of numbers, like:
{[%evp 0,96,30,30,22,1,30,2,2,-9,-3,-44,23,23,21,32,41,37,44,23,22,18,26,11,22,
-4,0,-1,8,7,7,14,9,5,16,8,38,16,22,19,25,54,19,19,22,22,22,20,20,20,24,-18,24,
-53,-53,-61,-61,-56,-23,-20,41,41,39,39,35,30,44,44,33,50,70,70,75,75,75,75,75,
56,60,59,62,56,68,56,50,48,48,40,46,60,49,30,48,47,47,59,46,56,57]}
I assume ChessBase 15 generates this when it quickly analyses games when you open them. However, is this a standard PGN code, can other chess programs read it?