Here's a coupleThe trade of 1 share indicates a cross of shares,...

Here's a couple

The trade of 1 share indicates a cross of shares, generally between different Managed Funds within a Finance house. They need to prove that at the exact time of the move, that there was a trade at that price.

Another one depending on the price of the share can be a partially filled order that hasn't been executed.

Not sure if this is what you may be referring to.