5th Gear Main Shaft Tooth Count

[Luger]

Just bought an S4C 5th gear and in doubt which teeth to count on the main shaft gear since there are big and small teeth. Is it the big or small teeth that need to be counted to make sure its an S4C 5th gear?

Thanks

 

[Luger]

I counted the big teeth (I think these should be counted) on the main shaft gear which add to 32 but an S4C 5th gear should have 33 teeth......could this 5th gear been taken from another B series box with a 5th main shaft gear of 32 teeth?

Thanks