What's the meaning of "%evp" in a PGN comment? Example:

{[%evp 0,17,14,14,14,-25,-15,-15,7,7,55,48,48,48,472,228,802,802,804,771]} 
1. e4 e5 2. f4 exf4 3. Bc4 Qh4+ 4. Kf1 Bc5 5. d4 Bb6 6. Nf3 Qg4


What's the meaning of these numbers when used together with %evp?
A similar question was asked by GM Tony Kosten on the chesspub forum back in January:


  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?


The original PGN standard was created and published in 1994 by Stephen J Edwards. Here is a copy of his original standard: Portable Game Notation Specification and Implementation Guide. By 2001 he had dropped out of the project when this supplement was published to the PGN standard. There it defined a new embedded command string which would be marked by a starting "[%".


  3.2 A generalised format for embedding commands in comments.
  3.2.1 Position
  An embedded  command may occur at any position in a standard PGN comment, ie  between { } . For example: {Optional leading
  comments [%clk 1:05:23] optional trailing comments} where  [%clk
  1:05:23]  is the embedded command string.
  
  3.2.2 Structure The command string is structured as follows.
  
  A leading tag of [% A command name consisting of one or more
  alphanumeric characters. A space character. Either a single parameter
  or a comma delimited list of parameter values. A closing tag of ]


So, "[%evp" is an embedded command, first seen in Chessbase 15 output. As such it is Chessbase 15-specific until such time as Chessbase publish how they use it, at which time other pgn producers/consumers can start using it too.

My speculation, FWIW, is that it is part of Chessbase's "Chess Position Trainer" and is intended for Chessbase internal use only.