Automating Time Values on a Work Schedule (Rota)

Hi,

I'm trying to create a spreadsheet to run the rotas at work so that we don't constantly have to recalculate all the hours when we make a change. I'm trying to get the rota to understand that if I put 10- it is worth 13 hours so that at the end of the week it can add up the different values to give a weekly hours total.

The other values I need it to understand are (-10:30 means 3.5 hours) (A/L means 8hours) (B/H means 8hours) (x means 0) (M/L means 0) (9-5 means 8)

If anyone knows a way to do this it would be massively appreciated, I'm struggling with the fact the shifts are split across two days as its a children's home and we work over night.

I have tried to attach an image showing what I'm aiming for.