Encoder value before dentent

Hi,

I have tried to use the encoders solution on the forum but here is my problem.

I have a brainv2 and my encoder send those signals
Stop
7f
7f
7f
7f dentent

so befor the dentent (20ppr) it sends already 4 values so it's difficult to make adjustment since I jump of 4 values before the dentent. So I have tried to make a counter that takes only one of the 4 values but I dont know how to skip the first 3 ones and keep the 4th signals. Also I have read about the modulo that I could divide the 4 values by 4 to make one on the dentent but I would need some help.

so would it be more appropriate to use a counter that take the first 3 and skip them and let the 4th let go?

Thank you.