Tapco Mackie 6306 Mixer

Question about mic and levels

I have a new Tapco 6306 mixer and a Shure SM57 mic which I run to the line-in on my Audigy sound card. My question is about the mixer and the mic. I set the levels exactly the way the manual states but I end up having to turn my gain up to 100% which is +25dB and this just doesn’t seem right.
The instructions say to first turn main output level up to about 25%. Then it says to start turning the gain up on mic1 while playing your instrument or singing into the mic until the LED light starts blinking, well, I do this and it will start blinking right at 100%, then I turn the level of that channel up to 50% and I get sound from my pc speakers, but it just doesn’t seem right to have to turn my gain up all the way just to get a good signal to my mixer.
Any help would be appreciated, is this right? recommendations???

Rodney, is there a link to a manual somewhere we could look at? You sure it says 25% for the main? ???

It says to turn the main to 9:00 o’clock which would be 1/4 ways or 25%. Check out the following link, about midways down the page on the right is a link to the manual. I’d greatly appreciate any help.