When an amount is spread evenly over several months, each monthly amount is rounded. The sum of the months can therefore differ from the budget on the expense item by a few kroner. This is normal and has no practical significance.
Why does this happen?
A budget of NOK 100,000 spread over three months becomes NOK 33,333.33 per month. When each month is rounded, the sum doesn't always add up exactly. The difference is usually just one or a few kroner in total.
How to fix it
Go to Setup and Operation and open the expense item.
Go to the Cost price estimate tab. Redistribute with the icon next to Remaining rev. Cost price estimate and the button Distribute remaining cost price estimate evenly (in your setup, "cost price estimate" may be called "budget"), or adjust the amount in one of the months by a few kroner.
Save.
Good to know
Small roundings mostly even out over the project.
If the deviation is larger than a few kroner, it isn't caused by rounding. Check whether the whole budget has been distributed.