TT guidance regarding Office Expenses and Supplies contradicts sources elsewhere.

[pcmoan1]

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.

[TurboTaxSusan]

Your cell phone expenses can go either as part of your home office expenses, or under  Utilities (Line 9220).

Regarding office supplies vs expenses, as per the CRA:

Line 8810 – Office expenses
You can deduct the cost of office expenses. These include small items such as:

• pens
• pencils
• paper clips
• stationery
• stamps
   

Office expenses do not include capital expenditures to acquire capital property such as:

• calculators
• filing cabinets
• chairs
• desks

These are capital items.

Line 8811 – Office stationery and supplies
You can deduct the cost of items the business used to provide goods or services, for example, drugs and medication used by a veterinarian or cleaning supplies used by a plumber. If you run a daycare, these include household supplies that children use and food you buy to feed the children.

[pcmoan1]

You've provided guidance to modify the tax form directly, but I'm using the TT Web UI.   The UI provides me with the following options in which to enter expenses. Home Office, Office Expenses, Supplies, Miscellaneous Expenses,  + a whole lot of other choices.   

I'm not familiar with how a TurboTax web app user modifies the form directly, or why this would be the recommend approach.

I'm looking for guidance that pertains to the UI.  I assume cell phone bills would go under either Office Expenses or Miscellaneous Expenses.  At present I have them under Office Expenses.  No idea if that translates to your line 9220 or not.

[TurboTaxSusan]

The expenses in TurboTax Online correspond to what's on the T2125 form, because the CRA is going to get the form. There are sometimes differences in the wording because TurboTax is trying to be easy to use, while the CRA themselves are often not clear on what is what. 

Still, if you aren't going to claim your cell phone costs as a home office expense, then you can put it under utilities. You can find it in the expenses search by searching for "phone", or just go to page 4.