So... The past 3 months, inflation has been 7.24%

[progree]

9. AH HAH! AH HAH!! I know why the inflation calculator and my numbers don't match for the 3 months Dec'23 - Mar'24

The inflation calculator uses the NOT seasonally adjusted numbers
https://data.bls.gov/timeseries/CUUR0000SA0

All my graphs use the seasonally adjusted numbers
https://data.bls.gov/timeseries/CUSR0000SA0

BLS inflation calculator: https://www.bls.gov/data/inflation_calculator.htm
At the bottom of the page:

The CPI inflation calculator uses the Consumer Price Index (https://www.bls.gov/cpi/) for All Urban Consumers (CPI-U) U.S. city average series for all items, not seasonally adjusted.

(emphasis added)

For the purposes of the inflation calculator and for the closest to what people are experiencing, the actual (i.e. not seasonally adjusted) that you used in your OP is the more relevant one.

So, your 7.24% (annualized) in the last 3 months -- some due to seasonal factors and some due to non-seasonal changes, is the winner.

I'll have to, in the future, at least label my graphs as being seasonally adjusted.