No, your understanding was not incorrect. You can search for specific amounts, if these amounts exist as an Opening Balance or a Current Balance, as these are the only two 'amount' fields available to search on in the Column Editor for Ledger.

You said you found the fields you wanted, so I am assuming that they are one of these. To get the search to find a balance between say, $200.00 and $225.00, after you have pressed <F6> to bring up the Finder:
1. Select Current Balance or Opening Balance from the 1st search criteria scroll box (on far left of Finder window) by clicking on the arrow to the right.
2. Go to the next scroll box (middle), and select the "In the range of" option, again, by clicking on the arrow to the right of the scroll box.
3. In the next box to the right, enter your minimum value (200.00), press Tab, then enter 225.00 for your maximum search criteria.
4. Press Enter to start the search.

I hope this helps.

Regards,