The calculation of work-space-in-the-house expense is based on the workspace ratio when you indicate you have a dedicated workspace, and will consider hours worked when you work in a shared space.
You will indicate which situation applies to you at the top of the section titled "Line 16 - Calculation of work-space-in-the-house expense", and Turbotax will automatically calculate the employment-use amount based on this selection, the area details and hours worked, as well as the expenses entered.
Here is a link to the CRA's information regarding this calculation and how to determine your workspace situation, How the claim is calculated - Home office expenses for employees - Canada.ca
