The INS in the 1011 Captain II is basically the same Captain Sim INS as that in the 1011 Captain for FSX/SE/P3D3.

This from the manual:

Zero Drift Error Feature:
- data Selector
- DSRTK/STS
- press REMOTE
- when REMOTE illuminates you will see increasing digits on the left display
- press key 3
- REMOTE will extinguish
- if you press REMOTE again
- you will see 0

Drift error is erased and will not increase in the current flight.