What happens if my marriage visa extension funds dip below 400k during the first 90 days?

Good morning,

Question regarding marriage visa extension:

With the 400k requirement for the extension, what happens if, within the first 90-day stamp (pre-extension period), the 400k held in your account dips slightly below, without realising!

Eg: 400k held in an acc, but a bank fee withdrew without knowing for a few days, and pushed it to 399k until I could top it back up over the 400k – Does this mean that requirement would be invalid for the marriage visa extension, as we are supposed to hold the full 400k total in the account for "full 3 months" before the extension application?

Many thanks.