Time spent per page or visit metrics are expressed in milliseconds. However, you can create a Custom Metric ("Time spent / pages" or "Time spent / visits" divided by 60000) to display the result in minutes and then use it in your Data Query template.
You can follow the article below to have a detailed method to create custom metrics :
Note that it is not necessary to perform this operation for using these metrics in a Dashboard or Report, the conversion is then done automatically.
You can change it by clicking on “formatted data” in the option available in Data Query, for example :