Admin can set discount rules based on Cart total product quantity, Cart total price and Cart total products weight.

For making this discount rule select Discount Rules tab.
Now choose Cart Rules
Now you can choose Add New Rule as shown in the figure below.

Fill Rule, Restrictions and Validity tabs accordingly.

After saving the rule it can be seen in the given table below.

Now you have to give permission to your rule to give discount on the product you have chosen.
Click on the Setting Tab.
Check Cart Rule as shown below.

After checking these rules, Choose among First Match Rule, Best Match Rule or All Match Rule and click on save rule button below.

Now your Rules are active and if anyone buy the product which you have chosen they will get discount.

The Discount can be seen on cart page in cart totals.

Now whenever you want to disable this discount rule, you don’t have to delete it, just go to Setting Tab and uncheck this rule.