Thanks for your reply.
My opinion was that you start counting the 15 seconds as soon the start valve closes (eng master to off). Guess I am wrong?
I can understand that during a tailpipe fire priority is to crank the engine disregarding the 15 seconds limitation. But the exact same note is stated in the FCOM 3.02.70 page 7 in the ENG 1(2) START FAULT when manual start is aborted. This note makes no sense when counting 15 seconds after N2 reads zero.
Regards.