Unfortunately, Airtable provides no native ability to access any of the values that show up in the summary bar. You can’t access them via formula fields, nor can you access them via the API. (This applies to both the grouping information and the summary values themselves — both are off-limits to us.)
This is one of the big limitations of Airtable. I would highly recommend emailing email@example.com to ask them to please implement this feature in the future.
The only way that you can natively get “counts” or “sums” (or any other summary values) in Airtable is to link the records in your current table to other records in another table — and then you can create rollup fields to provide the summary information to you based on the linked records.
Otherwise, you’d have to do all of your grouping, counting, and summarizing on your own using some other methodology.
Similarly, I’ve also used Apple’s FileMaker to do this as well. FileMaker is an advanced database language that allows full programmatic access to summary information, plus programmatic access to an unlimited amount of sub-summary information (e.g. groups within groups within groups, etc.).
FileMaker also enables you to call API’s in other programs, so I’ve used FileMaker to bring records from Airtable into FileMaker by using Airtable’s API, and then I do all of the grouping & summarizing & custom reporting & custom PDF report creation within FileMaker.
FileMaker is an expensive tool, though, so it‘s not right for everyone.
p.s. I am a professional Airtable consultant, a Certified FileMaker Developer, and a Registered Integromat Partner, and the Integromat link contains my personal referral code. If you have a budget for your project and you’d like to hire an expert to help you with any of these things, please feel free to contact me through my website at ScottWorld.com.