The legend has been designed to fit the full description for all ShapeCodes being displayed, so the length of the longest description will set the size for all the Text in the Legend area. There are a few things you can try to improve this
ShapeCode Description Length
Reduce the length of the text displayed for ShapeCodes (note this is the description only, not the code itself). Try reducing multiple ShapeCode Descriptions i
Page Layout - Font Size for Legend Area
Try reducing the font size of the legend area in the page layout (FILE>PAGE LAYOUT)
Adjust Size of the Legend Area
Try making the legend are wider in the page layout, if using a vertical legend or higher if using a horizontal legend
