It seems to be working fine. Are you multiplying the "monthly cost to you" by 48 months instead of 12? The hire period is 12 months regardless of whether you select "4 years"(own it later) or "1 year" (own it now) in the calculator. Choosing the "own it later" reduces the ownership fee.
Is it just me or is the cyclescheme.co.uk calculator fucked?
Any time I put a 4 year option in, the monthly repayments end up totalling way more than the full price of the bike.
https://www.cyclescheme.co.uk/calculator