Given that they have 4 Pokemon to begin with, you must be playing doubles. If you scout a trainer from there, their lead pair (so 1st and 2nd) will be the two that they send out as a multi partner. Florian in particular has a roster of 46 different Pokemon, which won't be the same each time you encounter him, but whatever his lead pair was in that particular battle will become his partner roster, and if you ever run into him again and scout him a second time, you'll lose access to that first scouted pair, as they'll be completely overwritten by the new pair from the most recent time you scouted the same trainer name.
In singles, you'll get their lead plus whatever they had originally rolled up second in their random team selection--which may not be what they actually sent out second. So you won't be able to tell which one of the other two Pokemon you'll get when scouting singles, except by pausing your challenge and coming back to attempt a new multi challenge and see what your scouts have there.