I think generally speaking 13-29 is normal, or close to that. Total serum at 702 is completely fine. Like rowdybrad said, your SHBG may be high (which they can test). Nettle Root Extract mimics test is a lot of people's blood so that is a super cheap way to raise bioavailable test and if it doesn't work, you're out 8-10 dollars.
Good luck!
*edit
Also, time of day/previous activity/previous food intake/previous day activities may have effected the bioavailable test. Multiple tests on the same day would be more accurate... but not very cost effective haha.