Fiance Visa mistakenly rejected, stuck in appeal process

My fiancees visa to the UK (I am British citizen, she is Turkish citizen) was rejected 31/12 due to a mistake made when calculating my gross monthly/annual salary. My gross salary does exceed the minimum requirement of £29,000 but from the 6 months worth of payslips I had to submit for the application they calculated a net figure instead due to how the company I work for generates their payslips. This was the only highlighted issue which we immediately raised as a mistake and were told to exercise our right to appeal which we did. We're just wondering if anyone has had experience of appealing a decision and the time-frames for having it resolved. Timeline so far: Priority visa submitted - 18/12/24 Visa rejected - 31/12/24 Visa decision appeal - 7/1/25