So the reason for the difference is that the sizing spreadsheet you attached is sizing everything based on DAYS of data. The example you provided from the document, sizes most items based on ROWS or EVENTS.
You can change the sizing spreadsheet to rows simply by clicking the dropdown and choosing ROWS rather than DAYS. Once you do that, you will be much closer. The numbers in the sizing guide are actually a little higher than you would expect. the numbers in the excel sheet have been calculated based on data from customers databases, but nothing will ever be perfect.
The spreadsheet sizes using DAYS because thats generally what customers ask for, rather than rows. In the SEPM log retention criteria, whichever value is met first is what will be used (eg 50,000 events or 60 days) - in general with the defaults enabled, the event count will be met long before the day count.