Abhishek,As you mentioned that in ECC OMSL tcode the length is 40 which is by default should be 18.So i believe they have get it changed through modification kit available.You can also check with the functional team regarding this information.
Can you also check the entry in the table TMCNV in source system and see what value has been mentioned there.
Also check this note 83020.
Regards,
AL