As @Alexd1985 mentioned it’s related to extended data. As Yoroi uses results from Adapools the extended data is the following:
https://a.adapools.org/extended-example
You don’t need to include everything, buy you can specify values you are interested in.
Implementation is described in the first line of that document:
…in other words, in your pool meta-data document you add an extended json field that points to the document with extended data.
Example:
