The dimensions seem to be 270 gallonsish. I'm by far no expert on this breeding matter, and only have read from multiple forums. A lot of them have argued that it depends, there were pairs that never bred in 300 + but once moved to a 180 gallon they bred. There are multiple claims that they have had success at 180 and below (as far as I've read), but it seems that alot of the similarities though, is that they had 3 stingrays in the tank, 2 females, 1 male.
So Im guessing that the taiwanese hobbyist are probably implying that this 4x3x3 is perfect to house 3 adult 13s?