Basis for calculating land registry costs - tips?

The choice not really, but if you first check various calculators online and in the end realize that it is quite a bit higher than expected, you do wonder ... and such a fee for digital sending certainly hasn't existed just since yesterday, yet you still can't find any reference to it ...

We were also unlucky. All invoices had already been paid, but just before that our land registry office made some changes and then the notary demanded this "Digitalgebühr" again. Not nice, but there are worse things.