What are you trying to achieve?

If I understand your question, this is a standard issue with delta elevon mixing and isn't really radio related. If you want 30 degrees throw on elevator and 30 degrees on aileron then with both at full throw you will have 60 degrees. There isn't any way it could be otherwise.

If you want total throw to be limited to 30 degrees and still be able to simultaneously get full elevator and full aileron then, be default, you will have to reduce your elevator and/or aileron throw to stay within the 30 degree total limit.

If you have 30 degrees of elevator throw and 30 degrees of aileron, but you don't want more than 30 degrees total throw then this can be done by limiting total servo throw but when you apply, for example, full up then moving the ailerons will result in only one aileron moving (as the other is already at its 30 degree limit).