Have you ever gotten bids for voiceovers where one seller quotes in time and one seller quotes in words? Or have you gotten male voices responding to your need for female voices? What you get all depends on what you ask for, right? A simple way to compare all the offers you get is to make sure that you provide these minimum bits of information in your request: word count, gender, language or accent.
I recommend word count over the length of your video because you’ll notice that every VO artist on Fiverr lists the words included in their gigs. Video time might have two word phrases every 10 seconds or it might be a rapid-fire pharmaceutical advertisement. Run time IS important, but that information needs to come after word count.
Make sense? Happy Requesting!