Hello I need help to make a stats that calculates the average of the sizing used in my bets on flop
The size of a player's bet on the flop is stored in the database field "cash_hand_player_statistics.amt_f_bet_made" (for tournaments replace "cash_" with "tourney_").
If you want the amount in BBs you can divide it by "cash_limit.amt_bb" (or "tourney_blinds.amt_bb" for tournaments).
For an overview of custom stats see the Custom Stats Guide
, and for a deeper discussion see Tutorial: Custom Reports and Statistics
(the latter was written for PT3, but the same principals apply to PT4).