My daily mandalas always start with eight arms. I've done some with six, especially in winter when I'm inspired by snowflakes. And I've tried a "ten", I found it difficult to deviate from my habitual drawing patterns. That particular grid layout just seems to "feel right" for me.
The Greek sage Pythagoras believed numbers had both quantities and qualities, that they were mysterious and magical. He conceptualized them as forms not just as numerals. Additionally, he believed the numbers one through ten were the foundations for all things, the building blocks of matter. In his system the number eight is a the doubling of four. Four represents the building blocks of the cosmos (four cardinal directions; seasons; elements; the human body, etc...) and doubling that number creates perfect harmony. Eight represents love; friendship; wisdom and creative thought.
I believe that those things are part of every mandala I draw. Each one comes from a place of love, creative thought and focused concentration.