Dive summary:

• Scoring high F-numbers – for floor flatness on the scale devised in the 1970s – can be a challenge in  certain circumstances that are no reflection on the work itself.
• One issue involves floor penetrations and projections that get in the way of measurement standards called for in ASTM guidelines.
• Another difficult situation can be surfaces that are broomed to achieve a roughened finish, such as for parking structures where traction is important and specified F numbers may be impossible to achieve.

From the article:

The American Society of Concrete Contractors ... brings attention to this issue by letting specifiers know that F-numbers should be lowered when there is not space for the procedures and equipment used to obtain higher F-numbers. ...