If you have a local NH you follow the altimeter setting rules and set local NH at the top of descent and leave the minimas as they are. You're only reuired to add 50ft to the minimas if you use the area NH, which you wouldn't do if you have one from the TAF.
The shaded box means nothing unless you have an actual NH - which must be obtained from an ATIS, AWS or AWIS.
...and for those who haven't noticed, a certain key on my keyboard is broken dammit!!