For top IIMs like IIM A, B and C you need to have above 92+ percentile to get a call and above 95+ percentile to increase the probability of your conversion. For other old IIMs like IIM K, L and I you need to have above 85+ percentile and 90+ to increase the probability of your conversion.

In case of IIM Shillong with 83.64 percentile, you can get a call for second round of interview and WSAT. Honestly, you are at the edge of cut-off and your calls from old IIMs majorly depends on your profile (10th, 12th and graduation percentage, work experience). As you are a male engineer and have only 6 months work experience so unfortunately, you won't be any more credit in your aggregate score which comprises of all the parameters with different weightages.

But you will surely get calls from most of the new IIMs. If you get a chance to sit in the 2nd round of WSAT and interview then make sure you perform outstandingly because on the final merit list maximum weightage is given to WSAt and interview marks.

All the best!!