P48013 How to calculate the start date with lead time variable

Hi,

in the document "E1: 31: How Work Order Start Date is Calculated for Variable Lead Time (Doc ID 881632.1) I have read that the start date is calculate using this formula:

 (LTPU.F4102 X UORG.F4801)/ TBC.F4102 + SETL.F4102 + QUED.F4102

                     Work Hours per day from Mfg. constants (F3009)

Where LTPU: Lead time per unit from Item Branch table
           TBC: Time basis code from Item Branch table
          SETL: Set-up Hours from Item Branch table

         QUED: Queue hours from Item Branch table 

I use JDE 9.1 and I'm sure that the system doesn't use the field LTPU because I have change the value in the field LTPU a lot of time  and the work order start date is always the same.