for aspect of medicine i thought they were going for whether you want to be a primary care doctor or if you want to go into academia or something like that. that's how i plan to answer it anyway
for the page limits, i don't think anyone wants to read 3 single spaced pages for each app they read, but if you have that much to say, more power to you.
for MSTP i believe this is what you're looking for:
Please describe the basic and/or clinical research fields that you think you might like to explore and/or develop expertise in during your MSTP training. To the extent that you have defined potential specific future clinical interests, please describe the type(s) of medicine that you might be interested in pursuing once you have completed the MSTP.
Please note that these responses do not commit you to a restricted path if you are accepted to SBU; instead, they are used to help us connect you to the interviewers who can best address your potential interests.