B&K Precision 4052-4055 - Programming Manual - Manual (Page 6)

2
placeholders, of which there are two types: the header path
and the data parameter of a command.
:= A colon followed by an equals sign separates a placeholder
from the description of the type and range of values that
may be used in a command instead of the placeholder.
{ } Braces enclose a list of choices, one of which one must be
made.
[ ] Square brackets enclose optional items.
… An ellipsis indicates that the items both to its left and right
may be repeated a number of times.