This is an amateur opinion, so discuss this one with your doctor! However, be aware that many doctors seem to just pick a number off a wall chart. If you are a male over six feet tall, the charts are not realistic. Doctors know that, but may just write down what is there, hoping having a goal will let you lose some weight.

Let the Body Make the Choice???
Knowing this, it may make sense to simply try out new sensible habits for two weeks and watch the BioFeedback number before setting any goal. In other words, let the filtered response of the scale suggest a number for both you and your doctor.

Let the Goal Keep Adjusting???
Another possibility if your BMI is very high is to target an initial This is just a rule of thumb. Your body may tell you it can do better or worse.. 15% reduction in BMI and then lower it in response to the healing process.