Looking at San Siro seating map, doesn't look like strong sales. Playing the stadium not using typical goal end configuration (playing across rather than down pitch), which I am guessing would make capacity lower, maybe 40000. Maiden Italy website says more than 20000 tickets sold, which seems low but those ticket prices are high!
On Def Leppard website they have 2 UK shows listed as sold out but on Ticketmaster still a couple of hundred tickets left at both venues. Sold Out not always mean that.
Looking forward to other tour announcements this side of Christmas.