Help please - 9-day fortnight, annual leave conversion to hours

My company has recently introduced an optional 9-day fortnight, which I have opted in to, taking my daily hours from 7.5hrs/day to 8.33hrs/day.

To coincide with this, they have updated our holiday booking system from days to hours. I am not sure if they have mis-calculated the allowance.

Our year runs Jan – Dec, and the change took place on 1st May.

They have calculated a straight swap of 29 days x 7.5hrs (21 annual leave days, and 8 bank holidays)

Prior to the change, I had taken 10 annual leave days, and 3 bank holidays, with 8 days booked in the future, with the 5 bank holidays, leaving me with 3 days yet to book.

After the change, I only have 12.5 hours left to book.

I can’t quite get my head round the calculation, as I am not sure the 9-day fortnight compensates for the reduction in remaining allowance.

Are they correct? Or should it have been converted at 8.33 after the implementation date?

Thanks in advance!