How much does this damage degrade a note? [solved]

I have two notes that I bought as UNC and they each have a small amount of damage.

The first one is easy, it has a smudge or dirt or something similar in the corner:

Does that drop it down to XF?

Has anybody tried to remove a mark like that with a pencil eraser? I don't mind having a go because it isn't a valuable note.

The next one is not so easy. I bought it as UNC but there is a small corner fold that looks like the corner was stubbed. You cannot see it on a flatbed scan and it is very difficult to photograph. These are my best attempts:

Does that then drop to AU?

1. Such dirty spots are sometimes found on banknotes. I have Yugoslavia and Costa Rica UNC banknotes with these stains. I think this is a manufacturing defect. Never use an eraser on banknotes. This won't make it any better, it will only damage the paper. This will not make your banknote UNC.

2. This is a paper crease. This is an unpleasant thing, but not fatal. Sometimes such creases occur to bundles of banknotes. Still, the banknote can receive the UNC-62 grade, but this is not certain. If a high grade is important, then it is better to use a different banknote.

Thanks!

Does it mean then, to err on the side of caution, the smudged one I say is XF and the stubbed one is AU?

I think the first note is technically UNC. The smudge is not caused by circulation, but by the poor quality of the banknote's production. This is a common case. Here's a photo.

The second banknote is graded AU or UNC. I have seen notes with a slight crease at the corner being graded UNC. But for peace of mind, you can consider this to be an AU.

Thanks!