Calculation for Compute Savings Plan

Hi, question about Compute Savings Plan calculation:

I try to come up with some numbers and I'm not sure if I'm doing this right, so it would be great if someone could confirm. Let's say for example I have m5.xlarge instances that are all on-demand, and I pay currently $3000 per month for them.

I'd like to purchase a Compute Savings Plan, 3 years, no upfront for them and commit $1 per hour. According to https://aws.amazon.com/savingsplans/compute-pricing/ m5.xlarge has 40% savings over on-demand for that.

On-Demand cost 3 years: $3000 * 36 = $108000

Commit $1: $1 * 24 * 30.5 * 36 = $26352

$108000 * 0.6 = $64800

$64800 - $26352 = $38448

$38448 * (10/6) = $64080

$64080 + $26352 = $90432

Meaning over 3 years, I pay $90432 instead of $108000, because the m5.xlarge instances are billed with only 60% of their on-demand cost until my committed $1/h is used up. Is that correct or did I misunderstand how that's supposed to work?

Thanks,

Marc