REMOVE THE PRE-SELECTED $50 'MOST POPULAR' purchase from the buy screen.
there is also further down the screen a box showing $5 for 500 creds.
this is what i wanted to buy......what i got was $45 to much going into the coffers of wgt.
'SORT IT OUT'
It always seemed pretty simple to me. You put the amount you want to spend in the little box and click the button.