Tier2.year is a name for the year that vacation days turns from 14 to
21, or year 5.

Tier1.vac is a name for # of vacation days if time with co. is less
than 5 years
Tier2.vac is a name for # of vacation days if time with co. is greater
than or equal to 5 years

Disregard the names if it helps and just use the values, i.e. 14, 21,
and 5.