Denti, we have the FCOM version from 27 march 2009 for the NG , and for start is says:
" When N1 roatation is seen and N2 is at 25% or (if 25%N2 is not possible), at maximum motoring and a minimum of 20%N2..'
also
'Note: Maximum motoring occurs when N2 acceleration is less tahn 1% in approximately 5 seconds".