This is a really quick side note (rushes into classroom, scribbles on blackboard, throws photocopied pages at students, exits).
I came across this system first through The Gaian Tarot guidebook but it’s out there in the web-lands for the googling also.
As we are currently working through the Pentacles and on the pip (number cards) I thought it was a good time to mention it.
Working with numbers may be something you want to include as you grow into your tarot practice, I certainly find this additional layer can be useful. As noted before take what helps, what resonates with you, with your tarot magic, leave the rest.