No. If a budget figure was wrong at start-up, you can correct it directly on the production code in AIMZ. You don't need to re-import the estimate.
How to do it
Go to Prod. Codes and find the code with the wrong amount.
Open the production code and click the pencil on the card at the top. Correct the amount in the budget field (it may be called Cost price estimate).
Save.
Check the total row at the bottom of the table, and make sure it matches the estimate.
Good to know
Correcting the budget changes the starting point, without history. This suits cases where the figure was wrong from the start.
If you need to reallocate money later in the project, use a transaction. That gives you a revised budget and a log of what has been moved.
A new import may overwrite what you have entered manually.