Fixed assets setup - best practices

Hi All, what is the best practice to setup the fixed asset item on AX2012?

Currently I had setup the item as service + Stocked product, it have a lots of issue where system post the wrong cost and quantity to fixed asset.

For example:

I had purchase quantity 0.33 with cost 100,000 but system posted it as  0.41 with cost 8,900.

Do you guys have this problem before?