One Datafield Option below Climbpro, Segments, etc.

On the Map-Screen there is the possibility to chose one datafield below the Map, on the other screens such as Climbpro, Segments etc. I can only chose between 0, 2, 4. Why not 1? I would like to use some Connect-IQ Datafield (such as MapFields) there too. I dont see any reason why 1 Field is not available there...