that is related to your number of objects , for example , does your number of objects have three digit ?
or two digit and suchlike.
you can see random sampling table that it has many column, and we suppose every digit as a column ,so , let we have 300 object and we want to sample randomly 30 of them , ok.
for using random sampling table , you can start of any of columns for instance
we will start the first column on the left hand and then we will choice three column (every digit is as a column)
the first number is 670 since is greater than 300 then we betake it and we will see second number that is 371 .... finally the ninth number is 083 that is smaller than 300 then the 83th object will be the first member of sample and if we will follow this way then we will obtain 30 sample but if we read the first three column and we could not find 30 numbers we go to after three column and will repeat them again .
i hope you understand it