There is a difference between summing buses out of a mixer and the actual physical input level. Relevant input levels to output gain is where the summing mixer does it's job.
The StudioLive and StudioLive AI Series Console and Rack mixers are professional level summing devices. They take Mic/Line level inputs and place them in an output level that is sufficient for devices of it's kind (i.e. StudioLive AI PA, ULT or AIR speakers) including our Studio Series monitors which could have RCA inputs on them.
Concerning the AI series mixers, this mixer's tape output properly sits at a level of +18 db (which matches the other Auxiliary outputs) to accommodate any recording device including professional level recorders, with sufficient level output to the interface you are using. If the output rating is too low, you introduce noise into your recording source and it makes the device unusable.