Those two numbers were measuring different things. “Effective rate” was your all-in rate (federal, state and payroll taxes as a share of total income), while “Marginal rate” was just your federal bracket.

Both were rounded to whole numbers, so a 23.6% all-in rate and a 24% bracket would both show as 24%.

Both numbers were right, but their labels were too vague to tell them apart.

Coincidentally, we were in the process of updating the office home page and the all in rate is no longer displayed on there.