Yes, that is correct. They only draw the lottery for the top 3 picks, and then they are reverse slotted after that. So, the Lakers pick could only be 1-3 and then like 10 and on.
As far as we are concerned, the Lakers will finish with either the 10th, 11th or 12th worst record (they are battling Charlotte and Detroit). For the pick to convey to Boston it can only be 2 or 3. The odds would break down as follows:
10th: 2.9% chance of conveying
11th: 2.1% chance of conveying
12th: 1.8% chance of conveying