The note-size type indicates the percentage of the regular note size to use for notes with a cue and large size as defined in the type element. The grace type is used for notes of cue size that that include a grace element. The cue type is used for all other notes with cue size, whether defined explicitly or implicitly via a cue element. The large type is used for notes of large size. The text content represent the numeric percentage. A value of 100 would be identical to the size of a regular note as defined by the music font.
The
<note-size>element.The note-size type indicates the percentage of the regular note size to use for notes with a cue and large size as defined in the type element. The grace type is used for notes of cue size that that include a grace element. The cue type is used for all other notes with cue size, whether defined explicitly or implicitly via a cue element. The large type is used for notes of large size. The text content represent the numeric percentage. A value of 100 would be identical to the size of a regular note as defined by the music font.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/note-size/