The ZKTeco F18 access control terminal supports:
• Fingerprint users: up to 3,000 stored fingerprint templates (so it can manage around 3,000 users by fingerprint)
• Card users: up to 5,000 RFID/ID card templates (optional) if you use card authentication
So in practical terms it can handle thousands of users depending on whether they use fingerprints, cards, or both.