Question

How do you number chair conformations?

Answer 1

Unambiguously…?

Explanation:

And so you got a chair conformation....three substituents AXIAL and three substituents EQUATORIAL on each FACE of the chair...

Now of course, if the chair is substituted by other functional groups, the normal rules of organic precedence apply...

Clearly, the ipso carbon, whatever the substituent will be `C1`...

For `"cis"-1,4-Bu^tC_6H_10CH_3` here the carbon that is substituted by `Bu^t` is `C1`...and clearly `C-Me` is `C4` on the given scheme....and we would anticipate, reasonably, that `Bu^t` would be disposed EQUATORIALLY....as indicated on the given diagram...

And if you cannot see this on paper, I urge you to make a model...