address reviewer feedback

Author: guimachiavelli

learn/self_hosted/configure_meilisearch_at_launch.mdx

@@ -242,8 +242,10 @@ Meilisearch automatically collects data from all instances that do not opt out u
 
 **Environment variable**: `MEILI_CONTACT_EMAIL`<br />
 **CLI option**: `--contact-email`
+**Default value**: None<br />
+**Expected value**: an email address
 
-Adds the specified email address to Meilisearch's mailing list. Leave empty to automatically skip the email prompt when launching Meilisearch.
+Adds the specified string to Meilisearch's mailing list. Leave empty to automatically skip the email prompt when launching Meilisearch.
 
 ### Dumpless upgrade <NoticeTag type="experimental" label="experimental" />