the CRB entry for Signature Spells (pg 193) says the following:
You’ve learned to cast some of your spells more flexibly.For each spell level you have access to, choose one spell of
that level to be a signature spell. You don’t need to learn
heightened versions of signature spells separately; instead,
you can heighten these spells freely. If you’ve learned a
signature spell at a higher level than its minimum, you
can also cast all its lower-level versions without learning
those separately. If you swap out a signature spell, you
can choose a replacement signature spell of the same spell
level at which you learned the previous spell. You can also
retrain specifically to change a signature spell to a different
spell of that level without swapping any spells; this takes as
much time as retraining a spell normally does.
My question is about the bolded sentence-- does "one spell of that level" mean a spell with that base level, or a spell you've learned at that level?
For example: Summon Animal and Summon Construct are both 1st-level spells (or at least, their minimum spell level is 1). Say i have an Arcane Sorcerer who has added Summon Animal to his repertoire as a level 1 spell, and later added Summon Construct as a level 2 spell. Can he select both Summon Animal and Summon Construct as Signature Spells (i.e. SA for spell level 1 and SC for spell level 2)? Or do both spells still count as level 1 spells, even though one of them was learned as a heightened version?