You take a whole set of numbers, some of which are high, some are lower, etc., and you add them allll together, then divide by the total number of examples in the set.
This is also how inflation is calculated.
We take a basket of specific goods & services, look at how their prices have changed over time, then find the average increase or decrease across all of those things.
Cost of meals at restaurants is included in CPI.
Point being, McDonald's price increases are not 69 percentage points higher than "actual inflation". They are PART OF THE CALCULATION of actual inflation!
All this means is that other goods & services included in CPI increased less (or possibly decreased in price, lol) over the same time period.