Do the fireplace leg extension have minimums and maximums?

Yes, the leg extensions have minimums and maximums.

• Minimum – 4″ – Fireplace will arrive with legs set at lowest height, glass will be 10″ off the floor (11″ when using leveling feet)
• Maximum- 12″ – Fireplace with fully extended legs at max height, glass will be 18″ off the floor (19″ when using leveling feet)

Leg extensions provide additional 8″ of height (plus additional 1″ from leveling feet)

Telescopic Legs | Manual

If you or your customer desire a higher glass height, you can use the leg extensions in combination with a platform to raise the fireplace to the optimal viewing area.