This is the 500-image object-description track from RAWDet-7. It is object-level description with set-of-marks, not ordinary whole-image captioning: each annotated object is identified by a numbered black square with a white outline and a colored number, and receives its own detailed caption.
The release contains the exact 500 held-out images used by the paper, their corresponding full-precision RAW files, cleaned detection JSON, all 17 marked… See the full description on the dataset page:
https://huggingface.co/datasets/shashankskagnihotri/RawDet-7-Object-Descriptions.