SO WHAT, so it's just an adjustable reference point whose sole purpose is:
"This leveraged ETF seeks a return that is 300% the return of its benchmark index for a single day. The fund should not be expected to provide three times the return of the benchmark’s cumulative return for periods greater than a day." http://www.direxionfunds.com/products/direxion-daily-gold-miners-bull-3x-etf
Is GDX at 0?? NO. Will Direxion ever let it's products go to zero?? For as long as commodities and miners are worth even a penny, I highly doubt it!!