It is used to explicitly cast the type of a variable or constant (in the case
of numbers)

From the immediate window.
? typename(10#)
Double
? typename(10%)
Integer
? typename(10!)
Single
? typename(10&)
Long

In the instance you show, since the constant is declared as integer, it
seems a bit redundant.  It would more commonly be used to avoid a VBA's
implicit conversion when it causes problems.  

for example
? 32000 * 10
causes an overflow error (error 6) since both variables are treated as
integers

? 32000! * 10
320000
works OK becuase 3200 is then treated as a long

You might be more familiar with variable declarations that use a $ sign for
string

Dim i$, j$

rather than
Dim i as string, j as String

? typename(i$)
String