problem with quantity rule

Hi,
I have setup the rule like
min qty 1 then step 50
when I increase the quantity by +- on product page it selects first qty 1 the next step 51 the next step 101. Is it possible to set up as min qty 1 then on each + it selects the qty 50, 100, 150 instead of 51, 101, 151

Secondly is it possible to set the rule like open quantity after specific max qty i.e min qty 1 then max qty set to 100 after that customer can select 101,102,103…..etc.

Any help
Rizwan