The release type indicates that a bend is a release rather than a normal bend or pre-bend. The offset attribute specifies where the release starts in terms of divisions relative to the current note. The first-beat and last-beat attributes of the parent bend element are relative to the original note position, not this offset value.
The
<release>element.The release type indicates that a bend is a release rather than a normal bend or pre-bend. The offset attribute specifies where the release starts in terms of divisions relative to the current note. The first-beat and last-beat attributes of the parent bend element are relative to the original note position, not this offset value.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/release/