If you hover over the Save to Zotero button, you can see it's using the Embedded Metadata translator, which means it's using the metadata that the page provides. Unfortunately, that metadata can vary in quality. You can get the best data for that page right now by also saving using the DOI translator (by right-clicking on the save button) and then merging the two items in Zotero (select both, right-click, Merge Items), selecting the best fields from each version.

We're working on incorporating these generic translators into a single translator so that Zotero will automatically use the best data available from each method.