Question about Xiangqi equipment

I bought a chinese chess board, but now I realize that the squares are rather rectangular than square - 4.79 by 4.41 cm.

How regular is this? I kind of expected that horizontal and vertical distances would be equal, with as a consequence that the total board would not be square of course.

http://www.ebay.com/itm/WOOD-BOARD-for-CHINESE-CHESS-XIANGQI-LARGE-20-in-FOR-1-to-1-in-PIECES-429-/252436184879

I received an answer from the ancientchess.com and I guess I'll stop worrying and start playing on it.

"I understand what you mean about the board. I have been getting these particular boards from China for several years now, and they have always been like this, with the vertical lines spaces a little more widely than the horizontal lines. I have not read any specific information about this, but I understand it to be a normal degree of variation. I can only say that from my own experience, I have sold perhaps 200 of these boards over the past ten years, the majority to native xiangqi players, and have never had any complaints or questions about this aspect.