Malti,
Measurement & Automation Explorer (MAX) loads calibration constants from SCXI modules for use with virtual channels. However, the SCXI-1100 module does not have an EEPROM, so MAX is unable to load any calibration constants for it. This leads to the offset that you see in readings with your virtual channel.
In order to compensate for any offsets, you can use the SCXI-1100 Thermocouple.vi example, which uses the calgnd channel(for compensation).
Good luck with your application!