The size of the number boxes depends on the size of the font. Select the text in the box and use the font dialog. Choose the font you want e.g. Courier New and set the size. You are not restricted to the select box for setting the size, type the size in.
If you use Courier New with a size of 256pt you get a number box with the hight of 264 pixel.
Waldemar
Using 7.1.1, 8.5.1, 8.6.1, 2009 on XP and RT
Don't forget to give Kudos to good answers and/or questions