Automations are triggered based on adding or changing individual records, not groups of records. If you do something to five different records that ends up triggering a given automation, that automation will run five times: once per record. While it may look like Airtable is keying in to the category of a given record, it’s just keying in to that specific records field options, whatever they happen to be.
Could you describe your automation setup in greater detail? Without knowing more specifics, it’s tough to offer specific suggestions.