Great work - thanks for making this service available for free.
Suggestions:
1) When manually enter value in the area selection boxes, area marked on the chart should be adjusted to match.
2) When saving the area, the area saved should be the area in the Area Selection boxes (currently it saves the graphic area instead). If you implement suggestion one, this suggestion would be taken care of for free.
These changes would allow fine tuning of the area after using the graphic area selection tool or direct entry without using the graphic area selection tool if you already know the coordinates you're interested in. Then you could save the area and restore it later as expected.
Jay