Commander Mulligan Improperly implimented

Currently in Forge when you play commander it applies the same mulligan rule as a regular magic match. This is incorrect:
903.8. The Commander variant uses an alternate mulligan rule. Each time a player takes a mulligan, rather than shuffling his or her entire hand of cards into his or her library, that player exiles any number of cards from his or her hand. Then the player draws a number of cards equal to one less than the number of cards he or she exiled this way. Once a player keeps an opening hand, that player shuffles all cards he or she exiled this way into his or her library.