I dont have the willingness to search the exact calcution. You could check out premierleague.com if you want.Can you give a reference for the exact calculation method of 'big chance', because just like xG it appears to be entirely arbitrary.
If none of these metrics can even agree on how they should be measured, then it's pretty stupid to base an entire critique of a player upon it.
I repeat: we may have created a bunch of chances, but if few of them are actually very good then it matters little. The service from the midfield has been more woeful than the finishing.
But as a logical person I would assume that this metric just picks out chances that has a higher than 0.5 xG attached to it( better chance of scoring than not scoring, like pens, or shots from close range etc that usually get scored by most premier league players more often than not)