NIFTY CAGR if you had invested at 2008 high or low

For study purposes, I am considering 2008 high at 6400 (JAN) and low at 2300 (OCT).

To calculate the CAGR, I am taking the investment period as 10 years (if invested at high) and the 9 years (if invested at low). This is because the high happened in Jan while low was towards the end of the year.

Further, I am taking current value of nifty at 9900 and assuming the year is over for calculation purposes.

The CAGR formula is:

The CAGR is:
- if invested at high: (9900/6400)^(1/10) = 4.5% pa ... horrible
- if invested at lows: (9900/2300)^(1/9) =  18% pa ... awesome

Here is the nifty chart (monthly)