Remember that 617 is jointly RN and RAF - including the CO/XO roles.
This (news from September 2020) suggests that six dedicated ASW cabs will be the norm:
The RN website has a news page on her forthcoming exercise:
Carrier Strike Group prepares for final test
The exercise, which will run for two weeks, will see the task group pitted against warships from NATO’s Standing Maritime Group 1 in waters off north-west Scotland to prove it is capable of undertaking high intensity operations against the most demanding adversaries.
In other words, an opposing force of fully armed surface warships, and submarines (quiet NATO SSKs), and aircraft. It will not be the last contribution to NATO made by the CSG in the next few weeks and months.