When using information about a timer as a condition in a rung there is a lot of information available. There is the preset value or the current accumulated value both of which are numeric values. These are shown as T4:X.PRE and T4:X.ACC respectively (X = timer number). (This is assuming the default file (4), obviously, depending on processor, higher numbers might be used). These would typically be used in comparison instructions.
The current status of the timer is available as bit states. These are Enable (EN) which gives the status of the line which allows the timer to function, Timing (TT) which means the timer is enabled but is still approaching its timeout, and Done (DN) which means the timer is enabled and has finished its timing. If the timer is enabled either TT or DN will be on but not both. If not enabled then none of these will be on. These are shown as T4:x\EN, T4:X\TT and T4:X\DN.
Your question was a little vague but typically the DN bit of a self resetting timer is used. I assume you mean a self resetting as one which uses an XIO -]\[- of its own DN in the enable line. The DN bit will be on for one pass through the scan. (I see Allen covered this)