Screenshot the View checks list in your exchange order before the delivery executive arrives, so you can match every deduction they make against it.
When you buy a phone on Flipkart with exchange, the delivery executive checks your old phone at your door. The value drops for faults such as a cracked screen, dead pixels, a bent or cracked body, a missing button or SIM tray, or a swollen battery. View checks, inside the order on My Orders, lists how much each fault takes off, so read it before the pickup. Hand over the charger and the original box with the IMEI on it together, or neither, because if one is missing, the executive does not take the other and the value can drop.
Some problems stop the exchange completely: a phone that does not switch on, a model or IMEI that does not match what you entered, or a screen lock or iCloud lock that is still on. Before the visit, back up your data, remove every screen lock, sign out of iCloud on an iPhone and charge the phone to at least 50%. Factory reset it only after the executive finishes the checks, because the executive cannot check a phone that was reset beforehand and does not pick it up.
If the executive offers a lower value, you can accept or reject it. Before delivery day, decide the lowest exchange value you would accept after any pickup charge, by checking what the phone would fetch if you sold it yourself.