There are two basic types of PLC counters: up- counters and down- counters. When an up counter has reached it's preset value, it will energize an output device and any associated contacts will change state. A typical down counter will count down to zero and energize an output. The Allen Bradley RSLogix down counter however counts down past a preset value, below which an output is turned off.

yes. for Counters this is Done Bit(DN or bit number 13 - c5:0/DN or c5:0/13 ).for CTD is set when accumulated value is equal to or greater than the preset value. if desired can be set XIC or XIO.
EQUAL instruction can be used to track a certain value. compare ACC value with your constant value.

Thanks, Toader!

with pleasure