I added the right amount of sulfite to my wine but the numbers are still low! – Vinmetrica – Sulfite (SO2), Malic, Alcohol & pH/TA tests for Wine, Beer & Kombucha.

This is a common occurrence with several explanations, any or all of which may be happening:

Make sure you are using fresh sulfite powder. Potassium metabisulfite degrades over time and that stuff you bought 2 years ago is probably bad now!
Make sure that you stir your wine thoroughly when you add sulfite. If you pour a 10% solution of KMBS into your wine, it sinks like a battleship! A sample taken off the top will read low unless the wine is stirred.
A significant portion of the sulfite you added may have ended up ‘bound’, particularly if your free SO₂ was very low to begin with. This bound SO₂does not show up when you measure free SO₂, and it is not protecting your wine. You will need to add more sulfite until your free SO₂ comes up to the right level. Sometimes you must add 2 or even 3 times more sulfite than you first calculated.