I don't know where you got your information from, but I have written testimony from one who was there, that between 1940/42 the gas chambers claimed some 300 lives PER DAY.

Addendum:

The book I was quoting from was given to my family in 1966 by the author, an ex Dachau inmate, has unbeknown to me been subsequently edited by the aforementioned author, to state that the Dachau gas chambers were not used as they were too small.
The unfortunates were transported to Hartheim in Austria to be gassed.

Apologies for any inconvenience caused.

PS

They were still gassed!