Product review (5 stars): Don't worry about length
I had the measuring all wrong. It really doesn't matter if the length seems too long.  The extender is magnetized to the outer edges of the sides of the stove and the longer length allows reach toward the backsplash. The black one matches my stainless steel stove w/black electric glass top.

If any tiny crumbs/flour/etc. fall in the small crack along the extender and stove, it's easy to pull up the extender and wipe it clean.