CPI is not a good indicator for overall inflation. It doesn't take into account everything. Now if you double it, it may represent more of a reality. :)
Better indicator of inflation was M2, which Fed discontinued after the massive printing during pandemic. Even M1 is, I believe around 13-14%.
More over, 15% is my personal observation.
M1 and M2 measure supply. This is tangentially related to price inflation/purchasing power and is absolutely not a superior metric to those that actually measure prices directly, regardless of the particular limitations of those metrics. It would be akin to saying that the change in supply of Hive from yesterday to today was a valid metric to measure the change in Hive price.