Changing the decimals in the order book changes the amount of digits to display past zero to a maximum of 8 decimal places for the price of an asset. Traders that wish to see and be more specific with orders may find this function useful.
In the examples below, a simplified order book is pictured. As you can see, as the number of decimals displayed is lowered the Amount, Total, and Sum columns are added together. If there were hundreds or thousands of open orders, this would be a way of condensing them to look at more data.
In our example, starting at five decimal places displayed the book can not be further condensed in this way. It will look the same until we lower the displayed decimals to two, at which point the remaining two entries are combined.