what is quality spread? please, someone, meaning, example, decrease

Kapie

what is quality spread?
There is an example in LOS 66j , that explains the stock return using multifactor model.It says, apart from other things, that a decrease in quality spread is good news for stock MT.

I looked up the meaning of quality spread ( Credit spread) but am confused as to how does reduction in quality spread is a good news for a stock and vice versa. Can someone please help me with an example here?

Thanks