What is correct "time offset" parameter for Zcash mining?

Start to mine Zcash on testnet. Everything works fine but in zcash-cli getinfo I receive that “time offset: -1” that is strange. Can anybody explain what “time offset” stands for and what is correct value? In blockchain explorer it is 0. Mine also was 0 but after several getinfo refreshes it changed to -1.

Using bas for Ubuntu on Windows 10.

for this and other doubt check bitcoin wiky very similar on core function