How to read it
What the number is
For each strike, the gamma of a unit of the option times its open interest in units, scaled to the rupees of the index that would need to trade for a 1% move in spot. It is shown in Rs crore per 1% move. Calls and puts of a strike are added with the signs the convention gives them.
Why three conventions
The open interest of an option has a buyer and a seller, and the public files do not say who they are. Convention A assumes dealers are long calls and short puts, the way US public data is usually read. Convention B assumes dealers are short every option, since customers in India are net buyers. Convention C uses NSE participant wise open interest to put a signed share on the dealing side you choose.
Zero gamma and the walls
Zero gamma is the index level where the re-priced total changes sign, if it does. A call wall and a put wall are the strikes with the largest call and put gamma either side of spot. A wall by open interest is shown next to them because that is how walls are often quoted, and the two need not agree.
How to read it
Read the three rows of the comparison table before the chart. If the conventions disagree on the sign of the total, the story depends on the assumption, not on the data. The gamma exposure module derives the computation and the one on zero gamma and walls goes through its limits.
What it leaves out
Nothing in an NSE file tells you who holds each side of a contract. Participant wise open interest splits by category across all index options together, not by expiry or strike, and a category is not a market maker. The profile holds each strike's implied volatility fixed while the index moves, though volatility moves with the index in practice. Hedging flows depend on other positions the dealers hold, on futures, on their own limits and on how they choose to hedge. A GEX level is a description of a model on one day. It is not a support or resistance level, and no level here should be treated as certain.