sp500 return

I have an retirement account in vanguard sp500 index fund from my prior enployer.  no additional money.  no touch at all.

$415K in Jan 2014

$930K in Jan 2024.  

It said $366k from market gain and $134K from income return ( i think it is from dividend), total personal investment return $500K.  

Rate of return:  15.7%---What?  it took 10 years to double, that should be 7% rate of return, right?