Why do Banknotes have Pen Scratch Marks on them? [solved]

Some banknotes, from the 20th century and to modern days, have many ballpoint pen scratch marks on the front and back, like are they anti-forgery marks, or security measures?

Thanks!

Bank tellers, and people in general, have often marked notes for various reasons. Not so easy on polymer notes.

Once, I got a  batch of 60+ old One Pound notes from a bank  which almost all had numbers written on them. As the cashiers got them in they wrote the quantity of the notes in the pile on the top note, thus creating a running number! Very irritating.

Also, each totaled bundle of notes would likely have had the total written on it when they were being counted.

In modern times blocks of notes loaded into ATMs are sometimes marked with a diagonal line when being loaded so that the operator can view at a glance the approximate amount of notes remaining in the cassette.

All a nuisance to collectors.