BB - the total number of legs in the shaded cells’ occupants is twelve.
The trouble is that there are so many words for types of the thematic that many will appear by random, especially if reversal is suspected. Teg, for one.
If the ‘direct’ in the preamble had been ‘precisely’ or similar, it may have been clearer (though the addition of clarity is not of course necessarily desirable in a Listener preamble).