Shares
Shares is the service type where delivering accounts repost or forward a post, an action that often leaves no public number and is hard to verify from outside.
What counts as a share differs by platform and by service. It can mean reposting to the account's own feed, adding the post to a story, forwarding it in a private message, or pressing an external share button that copies a link. Those produce very different results, and a listing that only says shares does not tell you which. Read the description, and where it is silent, test with a small order and watch what appears.
The measurement problem follows from that. On many platforms the share count is shown only to the post owner in analytics, or not broken out at all, so there is no public number that both you and the panel can point at. Disputes then rest entirely on what the supplier reports, since the panel has no way to check and you may have nothing to check against.
Reach does not follow automatically either. A repost from an account with no audience of its own is a number in a dashboard, not distribution. If the reason for ordering shares is that a platform appears to weigh them in ranking, treat that as a guess about a system nobody outside the platform can see, and judge the order by what happens to the post rather than by the share figure.
The same word, different platforms
A recommendation reaching real people is a different thing, and the button means something different on each platform. A service that satisfies its order by forwarding a link in private messages has delivered shares in its own terms while producing nothing you or anyone else can see.