This is caused by the discrepancy between the trading price and the net asset value. It is usually a small number, within +/- 0.5%. But if you look at the daily changes, it may appear to be out of sync with the changes of the stock prices in the holdings.
Because of this, sometimes it might be helpful to use a limit order when buying an ETF, as a limit order can limit the price to a small range from the net asset value. You can find the net asset value of GFGF here: https://gurufocusetf.com/gfgf/