Incorrect. The McCall fight was at Wembley but the crowd was only 23k people in attendance.
“There was a crowd of 23,000 at Wembley Stadium.”
Oliver McCall vs. Frank Bruno
Here's another reliable source (ESPN) reporting the same number along with his biggest crowd in his career which was 40k as I said previously.
“His biggest crowd came against WBA champion Tim Witherspoon at Wembley Stadium on July 19, 1986. Hopes were high that Bruno would become Britain's first world heavyweight champion since Bob Fitzsimmons (1897-1899) but a 40,000 crowd was left disappointed as the Londoner succumbed to a 11th round defeat.”
From Rumble in the Jungle to Cardiff, the biggest attendances in boxing history | ESPN