Help with internal signal routing on a 6602

I need to do the following with a 6602:

GPIO (any) to RTSI0

4 Counter Outputs to RTSI1-4; doesn't matter which.

I have tried P0.0->RTSI0 and then CTR0-3 to RTSI4.  But I get an error that the resources required for the last connection (CRT3_OUT -> RTSI4) are being used by the P0.0->RTSI0 route.

What are the rules?  Acording to the routing chart, they are all possible, but I don't know how to keep them from bumping into one another.