They have pdf's with reports on their site.

In May 2019 AMFEIX fund generated a total return of 13.733% (after fees), during the same
period, the Standard and Poors 500 index (S&P 500) generated a negative return of 6.57%
therefore the difference between both investments is of about 20.31%. The fund outperformed
S&P500 by a difference of 20.30%, overall AMFEIX fund achived a total return in USD of 64.23%.

*USD net returns are given by the following function: [USD ($) = Fund net return + BTC net price change]

So, those fantastic returns are because of BTC price change and not because they are great traders.