Exporting a video from Premiere spits out incorrect quality
When you export with h.264 in Premiere it has two bars as you show. A target bitrate, and a maximum bitrate.

The target bitrate is after all, only a target, and if your video doesn't have enough movement or fast action then you won't get the full Mbps that you've set. Even lowering it enough to only export 12Mbps because your video doesn't have a lot of movement.

Exporting a video with more movement will yield 60Mbps or more, depending on your settings.