Grey = pieces of the file are available but haven't been downloaded to your computer
Dark blue = pieces of the file that have been downloaded to your computer
Light blue = same as above, but the download is currently in-progress
Black (gaps) = missing pieces
The number is also related: 4,405 / 4,465 means that the file consists of a total of 4,465 pieces, but Share can only find 4,405 of them. It changes to a percentage while the download is active. More directly, your first 3 files have stopped downloading because Share cannot find the remaining pieces in order to complete the file.
You can try changing around your cluster keywords (ドラマ, テレビ, 映画, DVDISO, etc) in order to find other "sources" by connecting to other peers. Or you can use a plugin like CacheDumpExEro to force-convert the file by filling in the gaps with 0's (which will obviously create problems for some files). Unfortunately, this is one of the weaknesses of Share: once a file starts getting old, pieces start to disappear from the network.
In the meantime, you should start keeping an eye on your cache folder. When Share converts a file after it's done downloading, it still retains a copy in cache (effectively taking up twice the space of the file). If storage isn't an issue, you can worry about this later (I'll spare you the details because the solution will seem a little arcane) -- just focus on getting the hang of Share. But be prepared to deal with this oddity sooner or later.