Setting minimum and maximum purchase quantities is really useful for controlling how many of a given item can be purchased at once, and in with increments.
To access this feature, on the product edit screen, untick the box labelled Can buy any quantity.
When this is unchecked you will see a new area appear below. To add your first increment, click + Add Increment.
Specify the minimum and maximum quantity range you desire, along with the preferred increments. For instance, if you wish for a product to be purchased in a minimum quantity of 4 and a maximum of 1000, input the following details.
To make sure no-one can purchase under the minimum amount of 4, you must then cover the range of 0 to 4 with the increment matching your intended minimum value.
To specify a fixed quantity for the user to purchase, simply adjust the increment. For instance, you can set it so that the user can only buy quantities that are divisible by 2, ranging between 4 and 100.
For higher values, you have the flexibility to set multiple increments. In this scenario: below 4, purchases are not allowed; between 4 and 1000, you can buy in increments of 2; and for quantities above 1000, purchases are limited to increments of 10 with no maximum limit.
