You must not be running a scrambled pin on graphene or your wouldn't have been able to unlock your phone.
Discussion
What is that? I’ve actually been thinking about how to make a pin with good entropy
Roll 10 sided die. Or roll anything bigger than 10 and throw away rolls larger than 10.
On GrapheneOS. I don't know if other versions of android have it. Makes the numbers on your login pin in a different layout each time.