The number of boxes per page in the list depends on the page size and orientation choices made in the Chart Page Setup window. And ... depending upon which version you are using of UFT, there were updates/fixes to the box chart options. The following information from the knowledge base may help you; but I don't see any further on the SIZE of the boxes.
Answer: Open the chart you want to customize. Use the toolbar at the top of the Chart window to modify the displayed chart. Choose the Edit Graphics button to change the overall design of the chart, the Edit Colors button to make color selections and the Edit Fonts button to change the fonts used. If you're using Version 3.0 or later, you can move the boxes vertically or horizontally. Position the cursor on the upper left corner of the area you want to select, hold down the left mouse button and drag a box over the section of the chart you want to move. Press the right mouse button and select Move, then drag the select to the new location. If the selection cannot be moved, a circle with a slash through it will be displayed.