Pierre makes a good point. Another way of avoiding this conflict would be to always start with timer #000 and counter #127 (or whatever the highest number is). Then, as you need more timers, use 001, 002, 003, on up. As you need more counters, use 126, 125, 124, on down. This avoids having to allocate a specific number of timers or counters beforehand.
Back when I last used Omron stuff, we were limited to only 48 timers and counters (C20s era), so you had to use them sparingly!
-Eric