What are question underscores used for?

A question underscore is used to designate the exact place where a times table answer is to be entered (Figure 5). Question underscores also designate the number of digits in the correct answer. For example, in Figure 5, the expected answer is a single digit number (i.e. 5) and for this reason, the equation answer is designated by one underscore (e.g. 1 x 5 = _).
If the expected answer was twenty five (i.e. a double digit number), then the equation answer space would be designated by two underscores (e.g. 5 x 5 = _ _).
Likewise, if the expected answer was one hundred (i.e. a triple digit number), then the equation answer space would be designated by three underscores (e.g. 10 x 10 = _ _ _).
Figure 5 A screen shot that shows how the Times Table Test app will provide underscores to indicate how many digits there are in an answer