This simply means that the 'effective' speed (properly exposed shadows) is ISO 80 when using HC110.

You should meter for 80, not sure if it makes a big difference though (that's only 1/3 stop less than ISO 100, and other inaccuracies (speeds and apertures are commonly changing in full or half stops for example)

<Edit> sound a bit redundant, there's too many people out there ;-)