To qualify it will need at least 5 reviews. It has to have at least that number of playthroughs for the system to be able to calculate an average time. There are also requirements that they haven't released to the public, so obviously I couldn't advise you there.
Also, for myself I find it very difficult to time my own missions. I know how long I take to play it, but that isn't reliable since I know where everything is and I know what the dialogue says. Best way I suppose is to ask someone to play it cold, with no prior preparation, and time them. For example: I've got a mission on the KDF side right now that I think should qualify as far as time goes, but doesn't. I don't know if that's cause the 20 people other than me who have played it have taken under 15 minutes or because of some other reason.
Hope that helps.
The Foundry Roundtable live Wednesdays at 7:30PM EST/4:30PM PST on twitch.tv/thefoundryroundtable "I would rather take a chance on getting a change made to the game through positive engagement than know for sure that I got a change made by complaining" -drogyn1701, May 14, 2014.