Installation of the fixed amount of mechanical costs, material costs can adjust their own?

How to say it, according to reason is deductible, but in fact will be given by the quota, the name: comprehensive consideration.

Because this deduction will not be able to pull the end of the useless equipment you want to deduct, then I used the quota and not to add? If you want to add, then how to price? So in most cases both sides will still go by the quota.