I understand what you are pointing out however....
Assuming that this 20k withdrawal was done recently, I recall (think it was uj) stating that the balance could be as low as 400k in the 2 months prior to changing from based on retirement to based on marriage.
Folk doing that I always suggest stick with the 800k for two months prior to application just to be on safe side..
If withdrawal was recent , don't think issue for the OP.