There is a stats which is appearing frequently lately in soccer websites, which is named "big chances created", probably taken from one of those companies making statistics from the matches. What does this mean and how it's counted? Obviously it doesnt mean assists, because assists is shown appart as another stats entry.
I don't think there is a quantitative definition of the 'big chance.'
Opta, sports statistics platform, defines a big chance as
A situation where a player should reasonably be expected to score, usually in a one on one scenario or from very close range when the ball has a clear path to goal and there is low to moderate pressure on the shooter. Penalties are always considered big chances.