Magic Casting Rules Disagreement, How does it really work? Options

[eightball1011]

This week we had our first run using new SR4 rules. I am playing a mage, so naturally I spent days reading over all the rules for mages before the game. There became a disagreement between the GM and I about how a certain spell was cast. I had hoped that someone on here could help resolve this issue before the next gaming session.
I was casting the spell Influence using 10 dice (spellcasting 5 + magic 5). I had 4 hits! The GM, reading the casting rules from SR4, decided that it was a successful cast. Then I had to re-roll those dice so that the Defender could make an opposed test. (This is where the problem came in) I thought that he would use my 4 hits to roll his Opposed test against, but apparently the rules seem to state a separate Opposed test. This doesn't seem correct. Apparently he only believes these rules to apply to Manipulation and Illusion spells. Can anyone set us straight? Do we have to re-roll so the defender can oppose? or do the original hits count as the target?

Thanks in advance.