need help understanding how to use the XRMToolbox for autoNumber attributes

I'm finally at the stage where I am ready to set up and test the auto generating portion of this project. I logged into XRM Toolbox brought up the autoNumber attributes app but now I am a bit stuck!

I found the field I need to use to autogenerate the project #. But I am a bit confused on what everything else mean and how to pull it in.
ex to use for testing purposes is: B1903700_EP where B will be constant for the country Brazil. the 190 is the year 2019, the 3700 will be generated as well, and the EP will be sporadic based on the case type (about 12 different options- see below)

the B I built in a field not shown on the form itself, but as an option set with B defaulted for the country. I'm confused by what to enter in the seed or sample number portion in XRM. Where do I edit for what I need?

regarding year B220 will stand for 2020, B221 for year 2021 and so on. I'm just confused where I enter this to get it to sync to the pattern.

Do I then edit inside the number format box? where the yyyMMddd is? Where do I find the country fieldbox that contains my B, I'm just confused once I get here.

Do I need to create something like this for each field I need to be part of the autogenerating process?