Clock not accurate

I dont know how this all works but I take the 2/3 train every morning and this clock is never accurate. Im talking about at least 2 minutes off. Even after work at Penn Station, the ties dont match up to the times in the station. Its accurate for some other lines but not the one I use the most. Any reason for that? Would be the best app if it was accurate. Especially in the absurd summer heat.

undrgrndfan about NextStop - NYC Subway, v2.4.2