Why can’t the output of the `DiscretizeRegion` function display completely?

mr = DiscretizeRegion[Region[Rectangle[{0, 0}, {Pi, Pi}]],    AccuracyGoal -> 4]   r6 = TransformedRegion[mr,     Function[{t,       p}, {2 Sin[p]^2 Sin[t]^2 + 5 Cos[p]^2 Sin[t]^2 -        Cos[t]^2, (4 Sin[p]^2 Sin[t]^2 +         25 Cos[p]^2 Sin[t]^2 - (2 Sin[p]^2 Sin[t]^2 +           5 Cos[p]^2 Sin[t]^2 - Cos[t]^2)^2 + Cos[t]^2)^0.5`}]]; Region[r6, PlotRange -> {{-1, 5}, {0, 3}}]  DiscretizeRegion[r6, PlotRange -> {{-1, 5}, {0, 3}}] 

Why can’t the output of the DiscretizeRegion function of the above code be displayed completely?

enter image description here

In addition, I don’t know how to change the display size of the uploaded image.