What do finger IDs mean?

[headbank]

In the README you have:

# This is needed and only works in 138a:0097:
sudo validity-sensors-tools.enroll --finger-id [0-9]

My fingers don't come with numbers printed on the tips, so how am I supposed to know which number corresponds to which finger?

I looked also for such information in the python-validity repo but I do not see it there either (and it does not have its own issue queue so I had to post here). In fprintd there are descriptive labels for different fingers referred to on the command line, so I assume there must be a mapping. What is it?

Perhaps you can address this in your README? (Or gently explain what I am cluelessly overlooking)