4 Parameters of Crosstab.Value()?

In the designer, up to 4 parameters are offered for the Crosstab.Value() function, but I’ve failed to find a description of them in the handbook or help. Anybody know what they are?
There is a mention that they are coordinates, but I don’t know in what order and why there are 4, not just 2.
For the fourth parameter, only a Boolean is accepted rather than a Number as suggested in the attached screenshot.

Clicking on the parameter value typed in the input control brings up a tooltip with the description.