Reduction Factor Horse Racing Win Markets

Dear Support Team, 

I am not sure what happens if a horse withdraws and a reduction factor is applied. It seems as if some variables are adjusted by the reduction factor, and some not. 

An example from Todays 19:40 Fairyhouse race:

Before withdrawal: 
11:51:56   Selection: Teofimo, initial expr.: 1 / last_traded - 1 / maxlt_30, intermediate: 1/15.50-1/15.50, final: 0.

Then a withdrawal happens
11:51:56   One or more runners have been withdrawn from market "Horse Racing / IRE / Fairyhouse 7th Jun / 19:40 Fairyhouse 7th Jun - 1m4f Mdn": Ozark Daze
reduction factor was 35.34%

After withdrawal:
11:52:56   Selection: Teofimo, initial expr.: 1 / last_traded - 1 / maxlt_30, intermediate: 1/10.02-1/15.50, final: 0.03528427.

It seems as if reduction factor is applied to last_traded, but not to maxlt_30.

How can I modify the above expression, so that the result is zero after withdrawal, and also zero 30 minutes after withdrawal in case last_traded does not change? I know market variable reduction factor, but this does only work within the first 30 minutes after withdrawal. 

I am looking forward for any hint!

Kind regards,
Martin