Google Webmaster Trends Analyst John Mueller wrote a detailed post on Google+ explaining how the Search Console reporting works and why it may seem delayed for some of the reports.
The short answer is that it takes time for the data to get to the Search Console because of (a) the time it takes Google to send the data from the crawling department to the search console department and (b) the fact that different URLs on a site can be crawled less or more frequently.
Here is how John Mueller put it, so it is crystal clear:
When it comes to the aggregated reports in Search Console, there are two time-elements involved that are good to be aware of:
If Google doesn’t show my site’s AMP errors or hasn’t picked up that we fixed some of our crawl errors yesterday, it’s simply because of time delays in crawl and report delivery.
Many webmasters already know that the Google Search Console data is delayed by two days or more; this explains why that is the case.