Which includes blackbox modifiers like "hedonic adjustments". So if it costs you $800 to get a cast for your broken leg today as opposed to $400 a few years ago, but they claim the quality of the cast is twice as good, then they say there was 0% inflation as you are getting the same "value" even though its costing you twice as much to fix the same problem.

https://www.bls.gov/cpi/quality-adjustment/home.htm