EV104 = Elapsed value... of a timer or counter number 104. The current values usually decrease from SV (Select Value) down to zero. May also be accessed/read/erased/reload... like any general 16 bits word. In case of power loss: timers EVs are usually reset (those timers will restart from SV), counters EV are usually saved.
DT6113 = Data 6113. 16 bits word / general memory area. As for timers and counters the backup depends on your configuration and hardware.