When I give you a rule with a value, it is indicative, you need to adjust the value to whatever you need.
Weaver II pro had the exact same problem, and was using a fixed width as I just showed you how to do the job.
If you want you can use a min-width rule to give them a minimum width, but let them be bigger if you like (again use the value you like)
.menu-primary .wvrx-menu ul li a {min-width:100px;}