No, some very well respected aquarist believe the flush kit is a gimmick and really does nothing. Me personally...for the 8 bucks it cost me it gives me a little peace of mind, knowing I'm doing everything possible to lengthen the life of my membrane. Is this an in line TDS
meter? If its a hand held unit, it is most likely contamination from a previous sample, the vessel your using to test, or just dust, if it is an in-line meter then I find it quite odd that you have that discrepancy.