Hi Linda,
You basically need to try to make the column widths add up to 100% and they will self space within the limitations you provide. From memory, the % actually represents the minimum space that a column will use, but they will grow wider if other columns are not using their space allocation. So you could for example manipulate your example by adding a third unused column and making it 80% to try to bring the other columns closer, or make the width of the overall box smaller of course.
It’s quirky but that’s HTML for you.