Contacts and AI credits are two separate balances. Contacts are the data. Credits are the work: researching an account and writing the brief, researching a person and writing their emails, or turning a sentence into a search.
Free has no credits, which is why Sales Briefs and email writing are not included there. Starter includes 1,000 a month, Growth 5,000 and Scale 20,000.
Running a search, saving a list or exporting never uses a credit.