The Deployments Summary tab shows you the effective action that your deployment will perform.
It is very important to review this tab to make sure that at minimum the number of devices being impacted makes sense. This is your opportunity to sanity-check your settings before you update the model and commit your changes.
Note that no actions can be taken directly on the summary tab, but it gives you to overview to evaluate your deployment:
The tab shows the number of endpoints impacted, and the overall size of the deployment. Note that an explicit exclusion wins over an inclusion. (e.g. a device is in a group that has a payload assigned, but that device is also explicitly exluded means that that endpoint will NOT have the payload(s) installed.)