For brevity call your selection A

Your $10 back @4.6 yields

+$36 A Wins
-$10 A loses

Your $10 lay @4.5 yields

-$35 A wins
+$10 A loses

The combination yields

+$1 A wins
$0 A loses

A lost so you lost $0

If A had won you would have won $1.

After a maximum 5% commission you would have won at least 95 cents.

Thanks jfc thats how i had figured it out. Maybe there is some sort of mathmatics genes in me after all.
To me i think that was a pretty good bet. Couldnt loose and while i didnt stand to make much it was relativly risk free, im not sure what happens with late scratchings on betfair i presume money returned.