If you have already published a share schedule to several labels and want to then separate sharing to certain labels so that they have different options on the same release you can do this by extracting a label. This will create a new share specifically for that label preserving the same options and release.
- in Release Sharing find the share schedule you wish to split and click Edit
The Release Share Schedule will show what labels were selected to share the release.

- Find the label you wish to split out and click Extract.

A popup will ask you to confirm this.

- Click the Extract button to confirm.
That label will be removed from the current Release Share Schedule.

- Go back to Release Sharing. You will see a new Release Share Schedule at the top of your list of schedules.
It will have "Extracted:" appended to its original name to help you find it easier.

- Click Edit to view that new schedule. You will now be able to adjust that schedule as needed.

Note: if you just want to remove a label from an existing share schedule,
follow these steps.