Enter rent and calculate professional percentage

Dear Sir/Madam,

I would like to claim the rent for my flat, but I am a little confused about how to calculate the professional percentage since I am self-employed in secondary occupation.

I teach yoga classes and rent a small one-bedroom flat.
This means that 50% of my square metres are used for professional purposes, as my living room is my workspace where I prepare lessons, do my bookkeeping, etc.

However, as this is a secondary occupation, the amount of time I actually spend in this space for professional purposes is very low compared to the amount of time I spend there privately. Should I take this into account in my professional percentage here or not?

Thanks in advance if anyone knows! 🙂