AISC, page-5

Importance of Cut-Off Grade
I want to emphasize the control of Cut-Off Grade (COG) during the mining process to control All-In Sustaining Cost (AISC). Buss (2018) states, "Selection of an appropriate Cut-Off Grade is the most important and fundamental driver of economic value for any mineral deposit." This link will take you to 5 articles he has written explaining why Cut-Off Grade is so important.
If you have the flexibility to raise your COG you are able to drive down your AISC. This strategy is very effective for a mine to remain viable during cyclical lows in the gold price. Raising your COG results in mining and processing less gold ore to produce the same quantity of gold whilst maintaining your margin. Lower grade ore can be left in the ground until the gold price cycle returns to highs. Historical records confirm that an extremely high COG (circa 15 g/t) was applied to mined areas in the past. Th

Data released by SNG in their prospectus and subsequent Company Announcements confirm the occurrence of multiple high grade ore zones that would support the production of gold at a very low AISC if a higher COG was applied. This very low AISC is further underpinned by the proximity of these zones to the surface.

This data is well summarised by @Goldhunter122 in the following posts.
Post #: 49772919
Post #: 49774403
Post #: 49780263
Post #: 49781282