I’m sorry.. my eyes are somewhat tired today but I can’t see a footprint at all! I guess it must be one of those “trained eye” things.
Since they say the prints were in mud, my guess would be that they partially filled with liquid before the mud solidified. Thus, the flat bottoms in the depressions.
There’s one facing the lens cap.
Apparently the 800,000 year old human was wearing Keds.