Timers and counters are very similar, dont over complicate them, they are easy, have you looked at the help in the software its good info.
For counters say a CTU...when ever the rung goes true then it will go up 1 number in the ACC, you can address a RES to reset the count to 0
Do you have a question about them?, search this site, just type counters, you will come up with 1000's
if you see Ron Beaufort's name read the post...it will be good