Pr's four-minute video doesn't require you to have much material, but depends on how long the materials you collect add up to four minutes. And you can edit every material and delete all the unnecessary ones, so your material video is often more than 4 minutes. If your video footage is about 30 seconds each, then you need 8 footage. If your video material is 1 min, then you only need 4 video materials. So it depends on the length of your video material, not the quantity.