It looks like you've identified a common prefix in the IPv6 addresses on your office network, which is a good start. However, keep in mind that the first part "xxxx:xxxx:xxxx:xxxx" is just a subnet identifier, and devices within that subnet will have different addresses for the remaining sections.

To filter out visits from your office network in Google Analytics, you can use the "IP addresses starting with..." approach, but make sure to include the common prefix specific to your office subnet. For example, if your office network is identified by "xxxx:xxxx:xxxx:xxxx," you can set up a filter for "IP addresses starting with xxxx:xxxx:xxxx:xxxx." This should help you isolate visits from devices within your office network without affecting others in the vicinity.