You want to sync specific users from SF to IAS.
๐ First of all , are you using API 1 version? If so, then:
sf.user.filter | status in ‘active’ and username ne ‘yourusername’ | for active users and the specific one |
sf.user.filter | username ne ‘yourusername’ | for only the specific one |

๐ If you are using API 2 version, then
sf.user.filter=active eq “true” and userName eq “sf_username_placeholder”.
โญMore info at this link, where are available all the API reference