Semantics of "on" versus "in"

Please help me in choosing the right preposition in this sentence:

The returned values seem a bit confusing on/in its semantics,

Here I'm talking about returned values of a computer programming function, after reading its expected behaviour.

Which one should I use and what is the difference about using in or on?

Not all uses of prepositions can be predicted by meaning. There are very few prepositions in English and they have a lot of uses, so mostly preposition uses are arbitrary and governed by particular predicates (look at, listen to, speak on, tired of, etc).

That said, however, there is a very common spatial-dimension sense for many prepositions, including in, on, and at. As Fillmore describes it in his Deixis Lectures:

The preposition at is said to ascribe no particular dimensionality to the referent of its associated noun; the preposition on is said to ascribe to the referent of its head noun the property of being a line or a surface; and the preposition in is said to ascribe to the referent of its head noun the notion of a bounded two-dimensional or three-dimensional space.

Consider phrases like at the intersection, on the line, on the page, on the wall, in the city, in the kitchen.

Contrast

• at the corner, which means near or in contact with the intersection of two straight lines, or streets
• on the corner, which locates something as being in contact with part of the surface of some angular two-dimensional figure or three-dimensional object
• in the corner, in which the noun corner is used to indicate a portion of three-dimensional space -- in particular, a part of the interior of, say, a room.

Without context, I'm not sure what the sentence means, but it would have to be in their semantics (their because values is plural).

Can you restructure your sentence?

The semantics of the return values are confusing

or,

The return values have confusing semantics