Question on organic homework #17

[Grace_Stevenson_1A]

Could someone please explain why the answer key numbered the structure like so? (See picture correct numbers are in red). Don't you want the one that comes first alphabetically (butyl) to be one to have a lower #? Thank you so much! :)

[Nancyh_1E]

You number in the direction that gives all the substituents a lower number overall. If you started with 1-tert-butyl, the two methyl substituents will be numbered 3 and 4. However, if you start with the methyl labeled #1 in red, the two methyl constituents will then be 1,2-dimethyl. 1,2,4 is lower than 1,3,4 overall. If that makes sense :o You still name it in alphabetical order though, such that 4-tert-butyl comes first.