EDIT: There’s a Tab that says “Modified By” and then shows “Riding”.
The word “Modify” means:
- make partial or minor changes to (something), typically so as to improve it or to make it less extreme.
- transform (a structure) from its original anatomical form during development or evolution.
- (especially of an adjective) restrict or add to the sense of (a noun)
IMO, that means depending on your Riding Skill will the Mount Speed be “modified” to match your said Riding Skill.