Max width is image + effects.
Since your images are 124px and you want a 1px border on both sides, thats 2px so you need a max of 126px.
This can be fixed if you know where to change the subcategories span class.
What it should be:
Code:
<span class="subcategories" style="min-height: 149px; min-width: 124px; width: 126px;">
Edit:
The code will be likely found inside a {foreach} statement which produces each category.