Notary interest rate cost

Hi all,

I'm new at the forum sorry If I am going against any forum rules. 

My mother decided to buy a house in Amsterdam. She pretty much signed everything but according to her, Notary told her the payments for the house has to be done near to the day of sale in order to avoid additional interest costs.

So for example, if the house needs to be sold by the seller on the 15th of this month, then best to make the payment on the 15th in order to avoid any additional interest charges accruing in notaries account.

This is an issue because banks have daily transaction limits. thus payment has to be made in chunks before the 15th.  I just don't understand what these interest charges notary is mentioning.

Did anyone had such experience with these interest charges whey buying a house in the Netherlands.