Hi Barbara,
I am not an accountant so please do check with an accountant - but the calculations from the thread you quoted would work out as:
Total Mileage Claimed 93 miles @ £0.45 per mile = £41.85 - 0%VAT
Advisory Fuel Rate Reduction 93 @ £0.14 per mile = (£13.02) - 0%VAT
Advisory Fuel Rate Input VAT to be Recovered = £10.85 - 20%VAT
Hope that helps?