You have two options. The simplest is to create the new codes with the right budgets and delete the lump-sum item. If you want traceability, move the amount with transactions instead.
Option 1: Set the budgets directly (recommended)
Note the amount on the lump-sum item.
Create the new codes in Prod. codes, for example 601, 602 and 603.
Set the right budget on each code. On existing codes, correct the budget with the pencil on the card at the top of the production code, where the field may be called Cost Price Estimate.
Check that the sum matches the amount you noted.
Delete the lump-sum item.
Option 2: Move with transactions
Create the new codes with budget 0.
Click + Transaction in Prod. codes. In the New transaction dialog, select Transfer, the lump-sum item in From prod. code, the new code in To prod. code, and Amount. Repeat for each code.
The lump-sum item is left with the original budget and revised budget 0.
Good to know
Transactions give a history of what has been moved where.
If the lump-sum item has an expense item in Setup and Operation, you must delete that too.