How to make journald increase logs storage capacity

I would like to have persistent logs via journald. I created /var/log/journal and reloaded the service. Now logs are saved on the disk. But the log size limit is low.

I added /etc/systemd/journald.conf. (Storage=persistent/auto doesn't matter, I tried both).

[Journal]
Storage=persistent
#Compress=yes
#Seal=yes
#SplitMode=uid
#SyncIntervalSec=5m
#RateLimitInterval=30s
#RateLimitBurst=1000
#SystemMaxUse=
SystemKeepFree=10G
SystemMaxFileSize=1G
#SystemMaxFiles=100
#RuntimeMaxUse=
#RuntimeKeepFree=
#RuntimeMaxFileSize=
#RuntimeMaxFiles=100
#MaxRetentionSec=
#MaxFileSec=1month
#ForwardToSyslog=yes
#ForwardToKMsg=no
#ForwardToConsole=no
#ForwardToWall=yes
#TTYPath=/dev/console
#MaxLevelStore=debug
#MaxLevelSyslog=debug
#MaxLevelKMsg=notice
#MaxLevelConsole=info
#MaxLevelWall=emerg

As you can see I only changed each journal file size to 1Gb and told that I want 10Gb free on the disk.

But journald tells me that he only has 4Gb log storage capacity.

$ sudo systemctl status systemd-journald
...
jan 20 15:44:26 host systemd-journald[1218]: System journal (/var/log/journal/) is 4.5G, max 4.0G, 0B free.
jan 20 15:44:26 host systemd-journald[1218]: Journal started

What did I miss?

$ systemctl --version
systemd 229
+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ -LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD -IDN