Torrc modification doesn't work, even though Tor test page indicates that it does.

Operating System: TAILS 5.7
Tor Browser version: 11.5.8
Tor Browser Security Level: Standard

I modify torrc (/etc/tor/torrc) with the ExitNodes command. The Tor test page shows that this change was successful.

https://preview.redd.it/3hk99vx8du9a1.png?width=973&format=png&auto=webp&s=558952aa8c34f3907e104d84f6d650525ae19bd4

However, website info shows that my IP address is different from that shown on the Tor test page. This IP changes periodically, or if I reload the site. This happens on multiple sites.

https://preview.redd.it/6i5lh4z8du9a1.png?width=574&format=png&auto=webp&s=63aa90e3c488844679e29b19e99d9e622bc72bc2

What is happening?