I’m not sure if this will help or hinder, but the ‘official’ answer to this question as stated in the User Guide etc written by the site is that each observation must be for one and only one individual.
Under those rules if you held onto all 4 and photographed them together, to indicate your had seen 4, you would still need to do 4 separate records, adding the same photo 4 different times, and indicating in each that it was for one of the specific individual in the picture.
That being said, as seen in this thread and elsewhere on the forum, that rule is not one that is universally supported, not certainly not universally obeyed.