Basically when reading the value of a digit we start from the right.
Digits from the right to the left are named as follows:
units......>no zeros/digits after them
tens......> 1 zero/digit after the digit
hundreds.......> 2 zeros/digits after the digit
thousands......> 3 zeros/digits after the digit
ten thousands.......> 4 zeros/digits after the digit
hundred thousands.........> 5 zeros/digits after the digit
million........> 6 zeros/digits after the digit
Applying this on the above mentioned numbers, we will find that the 3 represents the hundreds (300) in 6300 while it represent the tens (30) in 530.
The question is to find the difference between the two, which means we will subtract them:
difference = 300 - 30 = 270
The value 3 in 6300 is 270 times the value of 3 in 530