Google indexed the canonicalized URL instead of the canonical URL
SOLVE
If the canonicalized URLs were already indexed before you added the canonical it's going to take some time before they're flushed from Google and attributed to the canonical instead. The "discovered" means Google knows about the page but has not crawled it yet; a page must be crawled before it can be indexed. Indexing times can range from 24 hours to 2 weeks. Search engine optimization never gives instantaneous results, it's a long process.
Google indexed the canonicalized URL instead of the canonical URL
SOLVE
If the canonicalized URLs were already indexed before you added the canonical it's going to take some time before they're flushed from Google and attributed to the canonical instead. The "discovered" means Google knows about the page but has not crawled it yet; a page must be crawled before it can be indexed. Indexing times can range from 24 hours to 2 weeks. Search engine optimization never gives instantaneous results, it's a long process.