Disability Benefit Question

[Guest lvegas]

I just read an old post about a disability benefit becoming 411(d)(6)-protected (i.e., not ancillary) to the extent it is greater than the "qualified disability benefit," which is described in 411(a)(9) as a disability benefit that does not exceed the benefit which would be provided for the participant if he separated from service at NRA.

For this purpose, do you simply compare the actual monthly disability benefit payment to the actual monthly retirement benefit payable at NRA, or is this a more complex, total benefit/actuarial calculation?