The -timing switch is a formerly documented feature, that still exists but is now undocumented. (I learned that fact from this interesting Undocumented Matlab post from @Yair Altman's great blog.) See his comments there.
But, I believe the short version of the meaning of these terms is
- item -- time spent on this line's item during startup
- gap -- (unexplained) gap between this line's time and the previous item
- total -- total of all items (including gap) up to and including this line
