TRONC including in financial requirement?

Hi everyone,

We have an employee who has asked for us to sponsor him when his graduate visa ends.
He is on a zero hour contract and receives house pay of £12.61p/h and TRONC of £3.45p/h. We would also need to promote him to a management position to make him eligible for sponsorship (however this is not a concern as he would have been heading that way in the future). My question is regarding whether TRONC is included in his salary calculations. With TRONC he is at £35,075 p/a , without he is on £27,540.24
I cant find a straightforward answer for a skilled visa route and every search takes me to family migration.