The effect is so variable that the reference range is nigh meaningless. Some people feel great at 300ng/dL. Some people experience genuine low-T symptoms at 650 that are fixed by bumping it to 1000. Some people are naturally over 1000 and have otherwise average hormonal profile (hair growth, muscle growth).

Also, the reference range is defined by an age span that is too wide to be useful, something like 21-59. The reference range is completely meaningless for a 25 year old man. Also the level varies drastically throughout days and weeks, so that one test is not a useful indicator of anything unless it's off the charts.

Basically, if you have low-T symptoms you should probably just get on T regardless of what number the test says. Find a doctor who agrees.