Capacitor measurement with specific conditions to understand that the capacitor is in a working condition
Get any old 100uF capacitor and measure it. OK so far? Place it in series with the 330uF and measure the series capacitance.

If the original reading was 100 uF and the 2nd reading was 76.74 uF then you can perfectly asssume that your 330 uF is exactly 330 uF.

Capacitors in parallel add like resistors in series but capacitors in series add like this: -

\$C_{TOTAL} = \dfrac{1}{\dfrac{1}{C_1}+\dfrac{1}{C_2}}\$

I.e. just like resistors in parallel.

Another test is to measure the leakage current and maybe you can measure the leakage resistance with your meter. This will give you some idea as to whether the cap is in good shape. If your capacitance is about right and the leakage resistance is over 1Mohm then there's a good chance it will be OK but there's no real substitute for trying it out.