“"In the UK and EU, dark chocolate generally contains at least 35% cocoa solids, although most products marketed as dark chocolate are 50–90%," says Ludlam-Raine.”
at least 35 % cocoa solidsabout 50 % cocoa solidsabout 90 % cocoa solids
“"In practical terms, a small portion of high-cocoa dark chocolate, such as 20–30g, can fit into a healthy diet, but there is no universally agreed amount that guarantees health benefits."”