Hi Antara 

It is quite obvious that to get a seat for sure, your rank must be within the total number of seats available for your category. But for convenience, it can be concluded that an All-India rank within 1000 will secure a seat in AIIMS MDS. I actually can't tell about the category rank but it will positively be a bit more than general but a rank within 1000 will surely secure a seat in AIIMS MDS.

Thank you