[3.P] The Summoner's Handbook: A Guide to the Pathfinder Summoner

[Barstro]

They must be the same kind, so I don't believe this makes any difference.

Allow me to explain;

Assuming you accept the premise that the caster gets to decide different locations for the 1d3 creatures (which I do not);

I do not think the spell means you summon 1d3 creatures as if you were making 1d3 attacks (A goes here, if there is a B, then it goes there, Same for C).

I think the spell means that 1d3 creatures are summoned (A at spot x, B at spot y, and C at spot z) if only two are actually summoned, then random roll to see if A, B or C is the one not summoned.

But this is based on how I read statutes. The makers of the game are probably not attorneys and may have assumed different things.