In the below code ? is used. ? is going to say whether label exists on the token or not. If label exists the expression works. Here my doubt is if label is not there what the expression is going to return
level = current.TotalSupplied? - current.TotalDemanded?
if (itemDependentDemand) level = current.TotalSupplied? - current.TotalDemanded?; else level = current.TotalSupplied? - (getinput(current) / getprocessflowvar(processFlow, "DepletionUnit", current.MainToken?));