the functionality to use formulas in custom item types is prone to an error.
We are using the custom field "Offer_TimeBugdet" with datatype "Number". The formula is "Offer-Timebudget-TimeSpent". When "Offer_TimeBudget" is 0 and TimeSpent is 64h (as example), the result is "-64h". That works fine in table view.
However, In the custom item type the result of the formula is 0 instead of 64h.