to catch a glimpse of one small part and from that infer the whole picture; to be able to judge the judge the overall situation from a single example

to see only a single spot of a leopard, describing a limited or narrow perspective on a situation

literally to see only one spot on a leopard; used to describe seeing only a small part of something and failing to see the whole picture

to generalize from a specific observation or to get a sense of the whole picture from a small glimpse; literally, looking at a leopard through a tube and seeing only one spot