It Is after all sync'd up to their "Cloud" and so should be able to sync back down if you change phones or need to do a full reset. Sometimes the discrepancy is so large (libre reading too low) that XDrip+ refuses to calibrate it (bey minimum value from the https://vuf.minagricultura.gov.co/Lists/Informacin%20Servicios%20Web/DispForm.aspx?ID=11352958