When your business accepts additional investment through overfunding, additional equity in the business will be released until your overfunding target is reached, or you choose to move your pitch into the completions process. Here is an example:
Amount raised | Equity released
£100,000 (target) 10%
£150,000 (overfund) 14.29%
£200,000 (overfund) 18.18%
The pre-money valuation remains the same but the post-money valuation increases with each new investment.