The Miscellaneous Information section contains 3 fields that let you further define an item.
The Found checkbox allows you to flag an item as being already found, or not.
The Tax popup is used to select the rate of tax for this item. Many states have different of sale tax rates, depending on the item being purchased.
The Upd (for update) field allows you to save the last date where you did a modification to that item. This information is to help you determine when was the last time an item was updated.
Finally, there is a last text area at the bottom that can be used to write specific information about an item and is called the Memo. This field is for your own usage.
Note: on the 120 and 130, since the screen is not long enough, the memo field is hidden, and an additional button will appear on your Newton to let you toggle on and off the memo view.