Yeah may be
But what even if they suppose give 80 calls for 70 seats and even 72 wer come for admission and even single have not chance to withdraw admission. And like u said if they just predict but what if the trend has changed due to some other factor.
Will u try to spend 200 rupee in advance as u know that atleast i will get 150 to pay back but from last 10 years i have got 220 rupee what if on 11th year u will get only 190 to pay back
well buddy .. they have these calculations which work.. and not only IIT K every college including IIM A gives buffer calls .. and I am yet to hear any1 given admissions and not taken into the college due to lack of seats .. So this is fairly fool proof method what ever they are using.
and not sure of IIT but some pvt colleges do have management quota seats .. so extra candidates if any will be accomodated in the management quotes seats that will be filled later after admissions.
This doesnt exist in Govt colleges i think ..but defintely in pvt ones.
sometime even after buffer calls are exhausted 2 waitlist also gets exhausted .