I don't think you missed them as this is mostly ingame jargon.
When creating rules for the game (Gameplanning section), you will see a Personnel area. This starts with 5WR, 1TE4WR, 2TE/3WR etc. So from there here is what a list would look like:
005 = 5WR
014 = 1TE/4WR
023 = 2TE/3WR
104 = 1RB/4WR
113 = 1RB/1TE/3WR
122 = 1RB/2TE/2WR
131 = 1RB/3TE/1WR (Currently not used, maybe a future enhancement)
203 = 2RB/3WR
212 = 2RB/1TE/2WR
221 = 2RB/2TE/1WR
230 = 2RB/3TE
311 = 3RB/1TE/1WR
Some of us got these from NFL coaches like the 212 which is employed by most NFL teams. Basically the first digit stands for number of RB's, the second digit stands for TE's and the third/last digit stands for WR's. But overall I think this mostly came out due to creating and editing of rules and trying to give a simple short abbreviation for each Personnel set. Hope this helps.