The value to display in the box. Usually a number or short text.
caption
The caption to display beneath the value.
icon
An icon for the box (e.g. "fa-comments")
color
Background color for the box. This can be one of the built-in
background colors ("primary", "info", "success", "warning", "danger") or
any valid CSS color value.
href
An optional URL to link to. Note that this can be an anchor of
another dashboard page (e.g. "#details").
Details
See the flexdashboard website for additional documentation:
<https://pkgs.rstudio.com/flexdashboard/articles/using.html#value-boxes-1>