The first setting we'll talk about is the one for orders under Settings -> E-Commerce -> Order Settings.
This setting controls what precision can be input on orders. So if you've chosen 1/32 in. (0.03125) as your precision and a customer tries to put in a number that doesn't fit into that precision then it will round to the nearest next possible value. For example, if a customer tries to give you a size of 24.4 inches the system will round it to 24.4062.
Since .4 is in between 12/32 and 13/32, it would round the value to the next closet thing - in this case 24 13/32 or 24.4062.
Note that because it's a web form it won't round the value until the order or bid is saved and it knows what number it has to work with. There has been some confusion when customers can't understand why the values change after they hit save.
The next setting to recognize is on number attributes. Number attributes are used mostly for size values. They have their own precision setting that is just meant to override the general setting mentioned above if for some reason you need certain attributes to have a different level of precision... and this is the same idea with parts. They have their own precision and it's to override the general setting on the Order Settings page!
To see the precision setting on an attribute open that attribute in the back-end catalog (Settings -> E-Commerce -> Product Attribute -> find the attribute in question).
Example:
To see the precision setting on a part, go to the product in question (Settings -> E-Commerce -> Products...) and then click on the parts tab of the product and open the part in question.
Example:
