Entering item details in Ampoule should be as quick and simple as possible. You can enter values manually, but you can also save you own presets that can be selected quickly.
Tap Custom Types and Units on the Settings tab to get started.
You can tap existing presets to edit or reorder them. Type in the field at the top to add new values.
Your custom values will be available options when you tap the list icon on the right of the Type field.
You can also do the same for the Units field, if the presets are not enough. Maybe you need something obscure like mg/mmol, kilodaltons or Becquerels!