High 40 cm
Please do not buy early Ming marked ceramics. They require advanced ceramics knowledge of the period, meaning glaze color pigment color, etc., and sometimes also some related historical facts. In this case looking at the mark alone decides it is a fake.
There are no Jianwen marks known at all. Even the existence of the reign itself was obliterated, originally. The reign was only three or four years and Jianwen was overthrown by the Yongle emperor before any marking of cultural items with his reign name could begin.