Walmart Inc.'s (WMT) - Get Report blowout earnings report Thursday morning resulted in big gains for upside option positions opened just one day earlier.

The afternoon of Wednesday, August 15, Investitute's market scanners identified the purchase of 4,600 August $97 calls for $0.13 to $0.18 with shares at $90. This was clearly fresh buying, as volume was well above the strike's open interest of 1,889 contracts.

Those August calls would expire on August 17, just two trading sessions after they were opened, and only one session after WMT shares would begin to price in the company's latest earnings report and expectations. After a year-to-date fall of 9.23% at the time those calls were purchased, these investors may have been materializing a belief that Walmart would see a better quarter, with a brighter horizon ahead.

Those August $97 calls traded up to $3.33 Thursday morning, more than 21 times their average purchase price. The stock rose 11.24% at the same time, showing how quickly options can far outperform their underlying shares.

Long calls lock in the price where investors can buy a stock, letting them position for a rally at limited cost with the potential for significant leverage. They carry less risk than owning shares because the most that can be lost is the price of the options no matter how far the stock might fall.

Walmart surged 9.33% to close at $98.64 August 16. The retail giant beat expectations on the top and bottom lines while raising its outlook before the market opened.