Ha, yeah - "fill numbers from left to right, from up to down" makes very little sense at all.
I guess you have to fill in only the centres you think are nucleophilic, but do it in order working from left to right, row by row starting at the top.
e.g.
if you had:
ABCD
EFGH
JKLM
and you thought C,F,H and K were nucleophilic you'd label C1 F2 H3 K4 and leave the others unlabelled.