Add calibration to G6 on xDrip+

Hi,

12 hours ago I put a new sensor in, and up till now it's always reading 1 mmol/l (18mg/sleep) too high. I've never had this problem before, so thought I'd just add a calibration. The only option I can find in xDrip is initial calibration though. What happens if I add a calibration through the initial calibration option? Does it just get added the set of data from the calibration done in the factory? Or will it reject that set of data and just go back to how it worked with the G5?