Zones - it doesn't like them

reserve zone 3
box 10,10 to 50,50
set zone 1,10,10 to 50,50
box 80,10 to 150,50
locate 30,0:print xgr,ygr
set zone 2,80,10 to 150,50
locate 10,20:print "MOUSE..."
while mouse key=0
  locate 0,0:print "Zone: ";str$(mouse zone)
  locate 15,0:print int(x mouse),int(y mouse)
  locate 15,1:print int(x hard(x mouse)),int(y hard(y mouse))
wend

This causes all sorts of slow down. It does eventually update, but very slowly.

Also, the xgr and ygr values are different to AMOS; 150,50 instead of 80,10