GBTC is a Bitcoin Investment Trust which allows big official players to invest into Bitcoin legally.
It is always a good indicator of future ie check my post that predicted price going down.
And currently, GBTC traded at 10 000 USD per BTC!
The math on this is a little bit complex, 1 share is 927USD and you need 9/100ths to meet whole BTC. SO adds up to 10k USD!
1 share is 0.09258535BTC right now.
If you are day-trading do what you want but id rather suggest playing leverage than selling/buying actual BTC ie at BitMex or SimpleFX.
We dont know when this will take off and would suck to sell and not rebuy. Of course decide yourself.