Both the above constructs return the value 8 as long as Number is within the above limits.
Generally speaking , the above construct is used when the month name is available in a cell , so that to get the month from the name is easy when all that has to be done is either :
=MONTH(1 & A1)
or
=MONTH(A1 & 1)
where A1 can have either Jan or January , Feb or February and so on.