CE effect "set keys" +/- N doesn't work when N > 4

[ncrecc]

Set keys - 1 removes the red key, set keys + 1 gives you the red key, set keys - 2 removes the yellow key, set keys - 2 gives you the yellow key... etc.
That all works fine and dandy, but in the editor, "set keys" can be up to 8:

When the number argument of "set keys" is 5, 6, 7, or 8, nothing happens, regardless of which keys are in your inventory or whether the operator is + or -. Presumably 5, 6, 7, and 8 should match to the 4 additional Emerald Mine Club keys (pink, skyblue, brown, and grey, named "key 5", "key 6", "key 7", and "key 8" in the editor), but + 5 doesn't give the pink key, and - 5 doesn't remove the pink key if you have it (and so forth).