TT guidance regarding Office Expenses and Supplies contradicts sources elsewhere.

TT tells me that office expenditures are "Small office items for your business" (e.g. pens) and Office Supplies are "Items you regularly use to do your work" 

Other sources of information tell me that office supplies are the tangible items I use and regularly replenish to conduct business in your office, including pens, paper, and printer toner. 
Office expenses, on the other hand, are items and services you use for your business that don’t fall into more specific deduction categories. They include cleaning services, general office maintenance, and some electronics and computer hardware.

Why does TT define supplies and expenses differently?  For example, I'm unclear where to record my cell phone bills.  I would think this would be under Office Expenditures - but that's where TT tells me to record things like pens.  

TT provides a list (in a PDF) of example costs, but does not map them up with where they get punched into the TT UI.