I'm not sure which airline you are referring to. If it is both underlined and italicised (as is the case for many airlines in O & I) the same booking class is used for awards and upgrades.

I notice a couple of airlines have an italicised booking class but not an underlined one in business or first class. I'd assume upgrades (underlined) come from the same booking class as awards.

The reason for the different formats is to highlight airlines where the booking classes for upgrades are different to those used for awards. A red underlined non-italicised code is upgrades only. A red italicised non-underlined code is awards only (except in business and first if there are no upgrade codes listed see assumption above). A red underlined and italicised code is for both upgrades and awards.

I hope this makes sense.