TDS Meter Calibration

I just got calibration fluid in the mail for the TDS meter I bought awhile back.

I dipped my meter in distilled water and it read 0 ppm.

I dipped it in the calibration fluid and it reads 783 ppm and the fluid is 1000ppm.

There's no where for a screw driver to go into this TDS meter soooooo NOW WHAT? How can I use this for water if it doesn't read accurately and isn't able to be calibrated?

Thanks-