n is an integer and n^{2} < 39

Quantity A: The greatest possible value of n minus the least possible value of n

Quantity B: 12

My Approach:

greatest value of n = 6.2

least value of n = -6.2

In the above case A is the answer but the answer is C

greatest value = 6

least value = -6

Hi! Can someone explain why n cannot be 6.2?

Thanks in advance