Understanding the spreadsheet/grid:
The colored headings at the top are the ranges of glucose values. They are color-coded to clue you in as to meaning.
Each day is 1 row. Each column stores different data for the day.
From left to right, you enter
the Date in the first column
the AMPS (morning, pre-shot, test) in the 2nd column
the Units given (turquoise column)
Then, there are 11 columns labeled +1 through +11
If you test at +5 (5 hours after the shot), you enter the test number in the +5 column
If you test at +7 (7 hours after the shot), you enter the test number in the +7 column
and so on.
Halfway across the page is the column for PMPS (evening, pre-shot, test)
To the right is another turquoise column for Units given at the evening shot.
There is second set of columns labeled +1 through +11
If you snag a before bed test at +3, you enter the test number in the +3 column.
We separate day and night numbers like that because many cats go lower at night.
The nadir is the lowest glucose between shots. There is a general period when it will happen which is specific to the insulin being used and testing then helps make sure your cat doesn't go too low.
It is merely a grid for storing the info; no math required.