6nct3-8hgpg-vy8h7-843w6-683gt- -

Another thought: maybe it's an invitation code for a service or an app. Some services use alphanumeric codes as invites. For example, "ABC123-DEF456-GHI789-JKL012-MNO345-PQR678-STS901". But the user's code is a bit shorter and has different structure.