Finance - Investment compounding at 19%

 Finance - Investment compounding at 19% ? pmI Looked at data presented  by Blue Trading - Track Record -  https://bluetrading.com/track-recordThey state that the average  compounded return is 19.08% per month since inception
At the end of 2016 (14 months since inception) the YTD is 590.90%
At  the end of 2017 (26 months since inception) the YTD is 870.05%The rule  of 72 - I used for my calculations.So what I don’t understand is:
If  the capital invested is compounding at 19.08% pm[?] then why is the YTD  only 590.90% at the end of 2016 and 870.05% at the end of 2017? (YTD =  Yield to Date?)
I presume that the invested capital is not being  compounded at 19.08% pm, because if it did, the investment would double  >6 times over the 26 month period and the return would be as follows:
1) To calculate compounding period in months
72/19.08 = 3.77. So every 3.77 months the capital invested doubles.
2) To find how many times the capital invested doubles over a 26-month period
26/3.77 = 6.89 times. So starting with $10000 it will double 6.89 times over 26 months as follows:
Starting with $1,000 and doubling at 3.77 month intervals we have:
After  4months $2,000/After 8 months $4,000/After 12 months $8,000/After 16  months $16,000/After 20 months $32,000/After 24 months $64,000 etc.I  used an online calculator to calculate the interest from the data  supplied. To increase $1,000 to $8,700 after 2.16 years comes to an  annual compound rate of 172% [26months = 2.16years]