MEO has used higher COS simply b'coz they believe in their DHI. Perhaps send an to Jurgen abt this, he's fairly prompt. The better the seismic data & its analysis the higher the confidence, nothing more then that. KAR did the same & came up with 28-32% back in the day.
Since MEO are the operator for Artemis & the farmour, I'd go by their calc's.
cheers
