GM will issue enough new shares so that the total number outstanding will be 62 billion. There are currently about 610 million shares outstanding. This is a dilution of 100:1. This will reduce the "par value" of $1.66 to $0.01/share. They will then do a reverse split of 1:100, reducing the outstanding shares back to 620 million.
The effect of this is that current common stock holders will be wiped out.
Example: you own 1000 shares which are currently worth around $1600. Your 1000 shares will become 10 shares, worth about $16. total. That's a loss of 99%.