In Chinese it's dian3, which is used as a time indicator (i.e. analogous to "o'clock"), and also part of dian3 xin2 (meaning snack, dim sum is the more common form in English but it comes from Cantonese). I'm not sure what it means in this context but this is just to say the pictographic analogy likely doesn't work because it probably is some unit here and not actually referring to the bath itself. That comes from the katakana which reads "Unit bath"