Minecraft wiki entry for Raw_JSON_text_format, associated text: NBT strings display their contents. Other NBT values are displayed as SNBT, with no spacing between symbols. If  interpret is set to true, the game will instead attempt to parse and display that text as its own raw JSON text component. That usually only works on strings, since JSON and SNBT are not compatible. If  interpret is true and parsing fails, the component is displayed as no text. If more than one NBT value is found, either by selecting multiple entities or by using a multi-value path, they are displayed in the form "Value1, Value2, Value3, Value4".