We can do this by sliding the counters up one full line. The columns were often grooved, so that the pebbles wouldn't roll away.
So how do you write 1 million in Roman numerals? Now we have to multiply by 3: just triple the number of counters in the copy.
There were many variations on the Roman counting board, such as extra columns for larger numbers. To find the overstrike character in Corel WordPerfect, press the "Ctrl" and "W" keys to bring up the tables of special characters, then go to the "Multinational" table and type "1,21" without the quotation marks to bring up the overstrike symbol.
Note that the Romans didn't worry about the subtraction principle unless they were actually writing their numbers down and not always then.
A pebble in the top half had its value multiplied by five. The first step is to make a copy of the bigger number,on the other side of the board.