I’m not sure if you’re joking or not, but the behavior of journald is fairly dynamic and can be configured to an obnoxious degree, including compression and sealing.
By default, the size limit is 4GB:
SystemMaxUse= and RuntimeMaxUse= control how much disk space the journal may use up at most. SystemKeepFree= and RuntimeKeepFree= control how much disk space systemd-journald shall leave free for other uses. systemd-journald will respect both limits and use the smaller of the two values.
The first pair defaults to 10% and the second to 15% of the size of the respective file system, but each value is capped to 4G.