change of Subcontracting Cost

Hi Guys,
We have Navision 3.7 with 5.0 exe and SQL Db. we have change log activated for all fields for Item. In my view the subcontract cost can be changed only when we run Calc. Standarad cost(we are using Standard costing). But in the change log some users names appears in front of modification of Subcon cost(although they never run this function).
How come?