When users create a new sub-account in Poolin, they need to select default currency/priority display currency, as shown in the figure below.
The reason why there is a default currency / priority display currency is that any sub-account registered in Poolin can mine all kinds of currencies. For example, if the sub-account created in the mining pool is test and the default currency set is BTC, then each time you click on this sub-account, the default/priority currency is BTC. However, you can also use this sub-account to mine other currencies like BCH, BSV, ZEC, LTC, DCR, DASH, XMR, ETH, etc. And you can view corresponding data.
More information about Default Currency, please refer to https://help.poolin.com/hc/en-us/articles/360032917412