Hi @Giga 

Great question! I'd recommend using a combination of linked records, Count fields, and formula fields to count the number of records from different tables and then sum them. Here is our Guide to formula, lookup, count, and rollup fields that may prove helpful! This community post also shows a great step-by-step by an Airtable power user on how to do this (even using specific conditions to count). Hope this helps point you in the right direction!