1) SG range for Jet A1 is 0.755-0.840. We are unable to measure this data ourselves.
2) Acceptable discrepancy is set by the operator. For example, my company expect maximum +/- 2% discrepancy [100x(actual uplift-calc uplift)/calc uplift].
3) If discrepancy > +/-2% and within 200kg (A320) or 400kg (A330), no further action required. Beyond these values, maintenance action is due.