The x-coordinates need to be subtracted and the y-coordinates need to be subtracted.
The x-coordinates are 6 and 2. Their subtraction is 6 - 2. Kendra did this correctly.
The y-coordinates are 8 and -3. Their subtraction is 8 - (-3) = 8 + 3 = 11. Kendra did this incorrectly. She should have had 8 - (-3) = 8 + 3 = 11. Then she'd square 11. Instead, she subtracted 8 and -3 incorrectly and got 8 - 3 = 5. Then she squared 5 when she should have squared 11.