Value units is the measurement scale of the data in the image. Value error is another slot for information about data quality. Flag value and flag definition allow for a special data value in the image. Not present here but sometimes added are comments about the file and lineage information, that is, where the data came from and how it was processed. The last group of items is legend information.
Legend cats gives the number of categories in the legend.
The actual legend entries follow. Here there are 134 legend entries, which you can scroll down to see. Not every attribute value in an image necessarily has a legend label. Here the value 0 has no label. Finally, a word about how Idrisi stores raster and vector data on disks.