TOC ISA and TDV in an OFP
Hi all, I would like to ask a question regarding some data found included in an OFP for a flight from FCO to BRU. In particular the OFP has a first FL STEP at FL380. In the first page I found that TOC ISA is M003, but when I go to the flight log page where is the TOC point I found OAT = M61, TDV = M04 and TRP = 434. So I have some doubt.
Following the rule to calculate the ISA deviation at FL380 it should be: (38*(-2))+15=-61°, so being the TRP (tropopause height) at FL434, why the TDV is indicated as M04, I was expecting that TDV should be 0? Also why the TDV at the TOC point is different from the TOC ISA indicated in the other page of the OFP?
Where am I making some mistake?