divide has four parameters :
1 - number from which divide should happen
2 - number to divide
3 - number of digits before the point
4 - number of digits after the point
and Round makes it to the specified digits.. in this case its 4, so it cuts till 4 digit depending on the fifth (if exists) digit, that is, if the 5th digit is >5 then fourth digit will be added to one.