SL/PE5 Rep Count

I have read a few threads about counting reps but I still haven't been able to determine the correct way to count reps for this exercise. 

 

This is the twisting arch up.  You do twist arch ups from the left and right.  Is one rep counted after both the left and right side is complete?  Or is one rep counted each and every time you arch up?

 

Thanks.

1 rep each time you arch up, so 5 each way

Oops, I did too much then 

Thanks.  I was counting a rep each time I arched up.  It looks like I was only doing half of what was required.  

It is still not clear what the correct answer is based on the various answers.   If it is one per each side - it is odd that there are some odd numbered sets. 

Just alternate which side you start on on odd sets. There's a forum post about twisting squats I think that mentions this.

Does the same rep count apply on SL/PE6 - Circle Arch up??