There are three scale factors: 1:1, 1:50, 1:100.
When opening a drawing in Model space, the scale factor is 1:1 by default.
When opening a drawing in paper space, it uses the sale factor of the first viewport in paper space by default.
Set current:
Click one factor to set it to be current scale factor in the list.
Add a scale factor:
Users could add a new scale factor by clicking “Add” button on the top right corner and entering a new
scale factor in the dialog box.
Delete a scale factor:
Long pressing on a scale factor or sliding from right to left , it prompts to delete it.