Fantasy Fooball League SetupLeague misconfigurations usually stem from the 'flex' posn setup.
Here is a BAD flex setup:
--#of flex plyrs: 2
--Posn for flex (checkbox): WR ---BAD
If you are only allowed to use WRs as flex players then it isn't really a flex (its fixed to only user WR). What Robo is asking is from what positions can you choose to fill the 'flex' position. If you can fill the 'flex' position with a WR, RB and TE (which is the most common way of doing it) then check the aforementioned positions.
Even if your league league officially only allows 2 WRs you should fill in the regular position chart in the way that a team is set up (on average) for your league. For example, if your league allows 1 QB, 2 RB, 2 WR, 1 TE, 1 DF, 1 K, 1 Flex (Incl. In Flex: RB, WR, TE) then usually teams will fill the flex position with a WR because they are more plentiful than RBs or TEs. So, in this example, you would enter in your setup as:
--Incl. in Flex (check): RB, WR, TE
Note that WR is set to 3 not 2. This will allow Robo to adjust RB, WR, and TE points for the 'flex' position properly and also to understand how your league typically operates.