Ruger 57 magazine capacity

[BraveBulldog21]

Hello, I'm new to the 57. I'm loving both of my Ruger 57s. I have the 57 handgun and the LC carbine as well. Nice that they share mags. However I noticed that the subsonic 55 gr reloads from Detroit Ammo fit 21 rounds while other manufactured rounds fit 20 like it's supposed to. Anyone else heard or noticed this?
Thanks, BB

[Buffman]

I've noted the Ruger mags hold 21.