According to the gigabyte website my video card should have a 1845 MHz core clock. However in MSI afterburner it shows the default is 2070. Is MSI supposed to report a faster core clock speed than actual or is there something up with my video card?
Nothing wrong with your card. This behavior is what nvidia calls "GPU boost." There is a table of core temperature/voltage/clock speed setting combinations in the BIOS that the card uses to determine how much voltage the core gets, and what clock speed it runs at, based on workload and temperature. At any given time, it will select what it thinks is the optimal combination from that table, subject to some tweaking you can do via Afterburner or Precision, to give you the best performance and power consumption. Most of the table features clock speeds greater than the rated "core clock."
What's listed as the "core clock" on Gigabyte's website is the minimum clock speed it will use unless the core temperature exceeds the "temperature target," which is the point at which it considers itself too hot, and slows down in order to cool off.