There are two different kinds of number attributes: integer and real number.
Number attributes can be used for instance to add tracking or serial numbers to objects.
Integer
Integer attributes are positive or negative numbers that can be written without a fractional or decimal component: ..., -3, -2, -1, 0, 1, 2, 3, ...
When no default value has been set, the attribute value in the diagrams is NULL. The default value is set by using a text field.
Real Number
Real number attributes are positive or negative, possibly non-integer numbers (decimal representations are permitted). They can be of type Single or Double, the latter allowing for more precision.
When no default value is set, the value 0 is by default visible in the Internal Block Diagram. The default value is set by using a text field.