My balance is 1390, but the unlock balance is 870
Why is the coin locked?
It's been a few days since we stopped mining.

Locked balance is coins that not enough confirmation (10 if you receive them from pool or other wallets, 60 if you did solo-mining). It also happens for the changes left when you send coins to another wallet but that may not be your case.
Please make sure your node is synced and try to run command
rescan_bc
from wallet prompt.