priority group activation

Your configuration appears to be correct for the desired balancing. Either the highest priority group pool member was unavailable, or the connections to lower priority group member originated via another Virtual/Pool (or via iRules).

"Less than 1" means no traffic is given to lower priority pool members, before 0 pool members are available from the highest priority group. You can try resetting the statistics to verify if your issue is still recurring.

This Manual seems to explain it: (Chapter "Priority-based member activation"): https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-concepts-11-1-0/ltm_pools.html1216212