The comma is used for separation of the two numbers listed. When we list two numbers, TT System suggest if playing a double-digit number like 885, you should also play it double 558.
Reason: Following TT system protocols suggest if a double digit number comes up in TT System equation, all doubles for that number posted should also be played. The first number listed is the main number expected to come out. For example, if the number 8895 came up in TT System equation, TT System protocols suggest you should also play it's double " 9985 and 5589". Another example, if the number 1113 came up in TT System equation, TT System protocols suggest you should also play it's double 3331.