Gifted Issues Discussion homepage Forums Identification, Testing & Assessment Please Help Me to Understand

Hello everyone and thank you for taking the time to read this.
I am new here and found this forum by googling my fingers off trying to understand and educate myself about my child's potential gifted abilities.
Recently there has been an article all over the web about a 4 year old girl (Heidi Hankins) joining MENSA. I did actually know what MENSA was so decided to read the article. I was surprised to discover that this child's testing score, media is regularly referring to her as "genius", and my child's test score (at age 5) are the same IQ 159. Though I have no idea if they took the same test.
My child was placed into gifted classes, and I wasn't too surprised by that. I have always known she was bright.
Of course, as a parent I was very proud to hear (and excited) that my child is considered over-intelligent by the test standard.
Now what I am trying to better wrap my head around, because I do not think I really grasped just what the scores meant, is how gifted are we talking here? How I understand it it, at some point there comes a fine line between gifted and LD. I mean to say, while one struggles to learn through a challenge, the other struggles to be challenged to learn. Either way, it is no easy road ahead.
In the article they referred to this other child as "genius", and said her tests scores (IQ) were one point away from Steven Hawking and Albert Einstein!?! this can't be correct?! Surely the likes of Steven Hawking must be off the charts?? like a 199 or something.
My child was tested using the Reynolds (RIAS) scale. There are a lot of abbreviations on the results paper and I am not understanding every bit of it.
Anything that anyone can break down for me, or help me to better understand would be so wonderful.
Are these types of assessment tests sometimes wrong? often wrong? and are they wrong to where they say a child is more advanced than they actually are?
To be honest, after my recent forced education into how potentially gifted my child might actually be, I have gone from feeling excited to more so fear and a feeling of, "I AM NOT QUALIFIED" I am reading so many comments/blogs/forum posts about high IQ tweens/teens becoming severely depressed. I want to do everything I can to keep the laughing, bright eyed, fun loving child through it all.... even through becoming aware of oneself as "different".

verbal Intell..... 154
nonverbal....... 146
composite intell...159 (%ILE>99.99;SEM=153-161, 90%confidence interval)

I would especially love to understand what the gibberish in the ( ) after composite is telling me? that there could be an error with the test?

"overall thinking and reasoning abilities exceed approx. 99.98%" ?! this seems pretty direct, but unbelievable?
There is also a mention in the paperwork results of a score for "motivation" This score appears much lower than anything else. Should I be concerned by that, could that be a sign of something more to come? Or this fairly common?

Thank you all for your time and help. I am sorry it is so long, but I so appreciate your time reading and responding. Especially if it can bring me a little peace of mind, encouragement, and education on the subject. I would also love to hear if others here share with their children their test scores, or the truth about being gifted. Obviously if in gifted they must have some clue, but like the child in the article, at some point (if not already) she will know exactly what her IQ is and what that means compared to others. Is this a good/bad/or neither thing for children?
thank you.