50 is an average ballplayer. He's 45+ overall, with each tool projected 50 or higher except in game power, which is a 45. His current defensively relevant skills (speed, throw, field) are all above 50.
I'm consistently mystified by scouting reports that break down most tools at 50+ and then rate the dude a 40, in line with the lowest of his ratings (and even if his lowest ratings are the most important ones). Either you grade the tools honestly or you don't. You can't have a dude whose game offensive metrics grade out at 40 and 45 and his defensive metrics are 55/60 with 55 speed (implying at moderate CF capability) and then give him a 40.
The raw grades they give you when applied to the real world translate to a guy who is - right now - a plus defender in the corners and an average CF with slightly below average hitting (.240-.250) and maybe 10-ish homers, with upside to .260 with 15-ish homers. In the real world, that current guy is a starting CF on many teams and the fourth outfielder on most others, not a 40 - which is the last guy on the bench - and the FV is an at least average regular.
In other words, that's a 45-50+ projection when you look at what it actually works out to. Whether I agree with their actual numbers is beside the point: their application of their own numbers to the real world is stupid. Either the guy has defensive carrying tools (which their numbers imply) and enough offense to stick and play (again implied by their numbers) or he doesn't, in which case you need to figure out why - and adjust the scouting numbers downward.
For example, right now the difference between that scouting grade and Robles at present is that Robles would be a 35 hit tool, 35 game power, and slightly rearranged metrics defensively. Which profiles to exactly what he is: a defensively capable outfielder who doesn't hit enough to be worth a lineup spot. He's a 40 right now: a guy who is good to have on the bench but you don't ever want him batting.