The answer to that lies in what the label on your panel states.
The panel will state where the half-size breakers are allowed as they are not allowed 'everywhere' or 'anywhere'. Some panels may not allow any half-size breakers. By "half-size breakers" I am referring to tandem breaker with one handle behind the other and dual breaker with handles next to each other, and, there are also quad breaker which are two half-size breakers connected together, typically with the inner two handles tied together and the outer two handles tied together, making for 2 double pole breakers in the space on 1 double pole breaker (by "pole" that is referring to - for simplicity - each full size breaker which mounts on a single breaker tab from the bus bar the breaker is connected to).
Let's see what you have to start with:
- Excluding the main,
- the panel has space for 16 full-sized breakers.
Okay, there are spaces for 16 full-sized breakers, which means there are potentially 16 circuits, which is reduced for each double pole breaker (a double pole breaker takes up 2 breaker spaces but is only 1 circuit).
The panel has a combination of full-size and tandem (split) breakers.
Which may ... or may not ... be allowed.
In the panel there are currently two double-pole breakers,
This means your available 16 circuits is now reduced to 14 circuits.
five full size single-pole breaks,
This means your remaining available number of breakers is 14 - 5 = 9 breakers.
The above breakers total 7 circuits: 2 double pole breakers for 2 circuits and 5 single pole breakers for 5 circuits. 16 potential circuits - 7 circuits used = 9 potential circuits left
and seven tandem (twin single-pole) breakers.
Therein lies the problem. It is possible that 'NO' half-size breakers are allowed. Only reading the label can answer the question.
Based on the sticker on the panel, the panel allows for tandem breakers and appears to have a maximum of 32 circuits.
You say the panel "allows for tandem breakers", would you post what the panel says, as the panel says it, or, better yet, post a photo of the panel label? That would help answer your question definitively. The panel label 'may' allow for 'some' half-size breakers ... 'may' ... or 'may not' ... or 'may but not in the locations yours are' ... or 'may but not as many as you have' ... it all depends on what the panel says.