The description for advancement Bullseye says "Hit the bullseye of a Target block from at least 30 meters away", meaning distance to target >= 30.

The advancement does not trigger at dist = 30, though. It only triggers when dist > 30.

See https://bugs.mojang.com/browse/MC-184271?focusedCommentId=711428&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-711428 - yes, the advancement triggers at dist > 30, but that is not what the description says. It should be "Hit the bullseye of a Target block from more than 30 meters away".