RE: Financial PutIt means that the BUK hedge is higher than the same time period natural gas price estimate being used by GLJ. So for example if GLJ figures gas will be $6 and BUK has a hedge at $7, GLJ is using $6 for the reserves report and working back to the NAV. Basically, GLJ is using the $6 for the valuation even though BUK will actually be receiving $7. In short, the NAV that GLJ provides is slightly lower than the actual value, all else being accurate. That said, the precision of the GLJ number depends upon how accurate their gas price forecast is versus actual prices received.
The "incremental value" simply indicates that the hedge is above what GLJ had expected the company to receive. 4.8 bcf is roughly 850,000 boe equivalent. As example, think $6 estimated price ($36 boe) versus $7 ($42 boe), which is say a $6 difference, or about $5M on the volume of the hedges.
GLJ posts its price deck here:
https://www.gljpc.com/pdfs/pricing.pdf