Generally speaking 100 is given as the mean on standardised tests, and the standard deviation is 15.
The normal distribution, or bell curve, describes many distributions, e.g., test scores, the number of hours a light bulb lasts, etc.
For the normal distribution approximately 34.1% of results will be between 0 and 1 standard deviations less than the mean (85 to 100), and 34.1% of results will be between 0 and 1 standard deviations above the mean (100 to 115).
And of course exactly half of scores will be above 100 and half below 100.
This graph shows the general distribution of normally distributed data:
www.mathsisfun.com/data/images/normal-distrubution-large.gif
As you can see, a score of 93, which is half a standard deviation below the mean, is around about the 30th percentile, so if you picked 10 children at random, 7 would have scored better on that test, and 3 would score at or below her level.
As for the non-verbal reasoning, this is highly correlated with the quantitative ability score, and a score of 121 is roughly 1.5 S.D.s above the mean, so this around the 92nd percentile, so only one child in twelve is expected to score better than this.
If your child has never done an NVR test before, then 121 suggests that she is very bright. If she has done any amount of practice, then my opinion is that the score is inflated, since you can coach for NVR quite effectively, however 121 is still a score that would tend to imply a higher score on the quantitative test.
It's worth noting that the 93 is NOT maths, but quantitative reasoning, which is designed to measure the ability to do maths, rather than any specific maths knowledge (more selective independent schools would tend to set an actual maths test, whereas it sounds like this school has done CAT scoring in order to understand where she fits in).
There's some info on the tests here:
gla.gl-education.com/sites/gl/files/images/Files/GLA510%20-%20CAT4%20Assessment%20Overview.pdf
See also:
www.nfer.ac.uk/nfer/research/assessment/eleven-plus/standardised-scores.cfm
www.gl-assessment.co.uk/sites/gl/files/images/Files/CAT_Primary_SR_20pp.pdf
This file shows correlation between CAT scores and GCSE results:
www.gl-assessment.co.uk/sites/gl/files/images/Files/GCSE_Technical_Information.pdf
Maths GCSE is most highly correlated with the mean CAT score (quantitative, VR and non-VR together), and both non-VR and quantitative scores are highly correlated with performance here, with a slightly, but not hugely, higher correlation to quantitative. A mean score of 105-110 (you don't mention VR score?), indicates that the most likely grade at GCSE would be a B.
So there is nothing particular to worry about IMO, even though she has an unusually spiky profile - it does look as if perhaps she has something of a mental block when it comes to numbers, even though she is generally good at non-VR/logic/maths-type stuff.
If you are specifically concerned about her maths, I suggest you check her KS2 maths SAT score. Past papers are available online, and it's very easy to mark.