Debbie,
You are correct. Keep in mind that time units for Medicare are calculated in tenths of a unit. For example, if your total anesthesia time was 72 minutes, then your time units would be 72 minutes/15 minutes = 4.8 units (not 5 units). Regardless, for Medicare, you report total minutes on the claim form, not units. If the anesthesiologist performed the service, then yes, your calculation is correct.
The reimbursement is different if the anesthesiologist provided medical direction or supervision. It would be helpful to review Chapter 12, Section 50 of the Medicare Claims Processing Manual:
https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/Downloads/clm104c12.pdf Other payers may have different reporting requirements and may calculate the units differently. Some payers allow extra units for qualifying circumstances, physical status modifiers, special positioning, and field avoidance (Medicare doesn't).
I hope this helps!
Sincerely,
Jennifer M. Connell, CPC, CPCO, CPC-P, CPB, CPMA, CPPM, CPC-I, CENTC