Fix typos in English explanation.

index.html

@@ -21,7 +21,7 @@ <h2>What is this?</h2>
     <li>Two people, Alice and Bob, sit in front of the same computer and open this page;</li>
     <li>Alice and Bob input their respective names onto the same page, and click "Generate";</li>
     <li>The page will generate two TOTP QR codes, one for Alice and one for Bob;</li>
-    <li>Alice and Bob scans the respective QR code into a TOTP mobile app, such as Authy or Google Authenticator;</li>
+    <li>Alice and Bob scan the respective QR code into a TOTP mobile app (such as Authy or Google Authenticator) on their respective phones;</li>
     <li>In the future, when Alice speaks with Bob over the phone or over video call, and wants to verify the identity of Bob, Alice asks Bob to provide the 6-digit TOTP code from the mobile app. If the code matches what Alice has on her own phone, then Alice has more confidence that she is speaking with the real Bob.</li>
     </ol>
     <p>Note that this depends on both Alice's and Bob's phones being secure. If somebody steals Bob's phone and manages to bypass the fingerprint or PIN or facial recognition of Bob's phone, then all bets are off.</p>