Writing out the full year uses 4 numbers so this takes 4 numbers * 6 fireworks per number = <<4*6=24>>24 fireworks.
“HAPPY NEW YEAR” contains 12 letters so this takes 12 letters * 5 fireworks per letter = <<12*5=60>>60 fireworks.
There is therefore a total of 24 + 60 = <<24+60=84>>84 fireworks lit at the start of the display.
From the boxes, they lit another 50 boxes * 8 fireworks per box = <<50*8=400>>400 fireworks.
So in total, the whole display uses 84 + 400 = <<84+400=484>>484 fireworks.
#### 484