Unless there is a sudden change at the end of the month (budget change or setting change), there is a 99.99% or higher probability that it will be within the budget. However, it is not 100% guaranteed. (We will adjust within the budget, considering that the medium will be used up to twice the set day budget.)
Also, if you have a very small budget setting such as several thousand yen per month, even if Shirofune sets the budget and bid amount to the lower limit that can be set for the advertising medium, the distribution pace will exceed the set budget. Sometimes. (In that case, the status "Budget cannot be reduced" is usually displayed on the Shirofune management screen.)
If you must never exceed it, please set it with a little margin, or if you have a media account, please use the media function to set the upper limit.