Is the RO
new? How long have you been making water? Are you absolutly sure the TDS
meter is clean and the cup your measureing the water in is absoutly clean. Even one or two bits of dust will affect the TDS
measurement. Your getting basicly 92% filtration out of your RO
unit at this point based upon those TDS
measurements. Usually a RO
unit is closer to 98-99% but I would also not shake a stick at what your getting.
Its best to run the waste as open as you can. Closing down the wasteline will shorten the life of the RO