If you purchased the item new in 2017, you will encounter the screen below after you put the type of asset, its cost, and purchase date. (See the attached screenshot below. Click to enlarge.)
Although, it sounds like you may have taken the annual election called the De Minimis Safe Harbor Election. This annual election allows you to expense assets that cost $2500 or less. When you expense the entire cost of an asset in 2016 you are getting a 100% write off. There is no need for section 179. TurboTax is taking you back to the main/overall business section because you must enter the asset manually/yourself into the Expense section using Other Miscellaneous Expenses. If you want to use section 179 instead of taking the annual election, you would need to say no to the annual election, then enter the asset in your Asset Summary and take section 179 when offered while entering the asset.
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