I fell into confusion because I was stupid enough to overlook a small mistake in the input data. This led me into believing that there was a big doubt in my understanding of the dual - primal concept. But I've realized my mistake and have posted the correct output result in the attachment.
As for people who would need a guidance in reading the solution of the dual from the primal problem, here are the steps I usually work out.
We start with the dual constraints corresponding to the starting solution of the primal. In this case, we have the 3 artificial variables A1, A2 and A3 as the starting solution variables of the primal.
The corresponding dual constraints are, x1<= M, x2<=M and x3<=M
Now using the property of primal-dual relationship, we equate the co-efficients of these three variables in the optimal primal table.
x1 -M = -M => x1 =0
x2 -M = 100-M => x2 = 100
x3 -M = 230-M => x3 = 230.
Hence the solution of the dual would be 0,100 and 230.
Hope it helped someone