If the difference was 20%, that's more than 16%, thus the next step up in the range options is WIDE. Even if you had one deck with 10% and the other to travel to the end of its range at 10%, the likelihood of you having that in the correct position for it to happen is slim. The system calculates the range at the most feasible option - WIDE.
It does a software pickup, so this still isn't a problem.