The box lists the maximum reach as being up to 10 feet - the box does not claim the extended product length to be 10 feet. On the back of the box on the specification chart, the product length is listed as being six feet, six inches, fully assembled.

Black & Decker's claim of a 10 foot reach is based on a conservative assumption that a six foot tall person could hold the handle at shoulder height (approximately five feet from the ground) and easily reach items to trim, 10 feet from the ground.  A taller person could reach higher.  A shorter person, by extending their arms further could also reach higher than 10 feet.