Check a section 143(1) intimation line by line. See which line the department changed, what the change is worth in tax, and the usual cause behind it.
Why does this page stop before telling me to rectify or appeal?
Because that is legal advice about what to do next, and this page is not doing that job. It reads the document and helps you understand it. Once you know which line moved and why it usually moves, you can decide whether the next step is Form 26AS, AIS, your deduction proofs, or a tax professional.
Why do you ask for both columns instead of just the demand or refund?
Because the demand is the effect, not the cause. A ₹6,000 demand caused by missing TDS credit is a very different problem from a ₹6,000 demand caused by income from AIS or a deduction being cut. The columns carry the cause. The final number does not.
What if every line agrees and the refund still changed?
Then the usual place to look is outside the lines this page reads: section 244A interest on the refund, or an adjustment against an older demand. The page names that shape on purpose, because silence there would read like a broken check rather than a limited one.
Why is TDS credit priced rupee for rupee and not at my slab?
Because TDS credit is not a deduction from income. It is tax already paid. A ₹5,000 reduction in allowed TDS usually moves the refund or demand by about ₹5,000 directly, which is why the page treats it differently from added income or a disallowed deduction.
Why do you rebuild taxable income from only some lines?
Because these are the lines this page is built to explain first: other income, Chapter VI-A deductions, tax, TDS credit, and the final refund or demand. The rebuild is not the whole return. It is a check on whether the figures you typed from the intimation still line up the way the two columns suggest they should.