Russ,
WELCOME TO THE AWS WELDING FORUM!!
As John said, basically, when measuring the fillet weld over a bevel weld you ignore any idea that the bevel weld is there and just measure the fillet weld as you would any other fillet weld.
Now, if the groove weld in the bevel was not full enough and it is actually wider than the leg measurement called for on the fillet weld then you have an underfill condition that will in many ways make the fillet weld larger in order to make it right. But if the groove weld was properly finished in the first place then, while you will see the weld in the bevel joint, the fillet can be sized as called out on the plans and per proper fillet weld gage usage.
Have a Great Day, Brent