It’s the Japanese equivalent of “cup” as a measurement unit, and at 180 ml is about 76% of a US cup. Japanese rice cookers are marked and filled in units of gō. You put n gō of uncooked rice in it, and then fill water up to the n mark. One gō is roughly 150 grams of uncooked rice, which amounts to around 530 kcal. Traditionally, a wooden box was used to measure one gō: https://commons.wikimedia.org/wiki/File:Masu,_One-Gō_measure...
A Japanese measuring unit for rice, kind of analogous to "one cup" in US kitchens. Measuring cups distributed with rice cookers are usually one gō in volume even in the US.
