What does The location specified for 'Data Files Location' has insufficient free space. mean?

I'm running a oracle DB oracle/database 18.4.0-xe in a docker container in a Ubuntu Linux subsystem on windows 10. I want to persist my datafiles locally so I don't lose my data when I stop the container. I use the docker command below.

docker run -d -it --rm --name oracleXe -p 1521:1521 -p 5500:5500 -e ORACLE_PWD="Password1_One" -v /home/user/opt/oracle:/opt/oracle/oradata oracle/database:18.4.0-xe

When I look at the docker logs I get the following error

[FATAL] [DBT-06604] The location specified for 'Data Files Location' has insufficient free space. CAUSE: Only (999MB) free space is available on the location (/opt/oracle/oradata/XE). ACTION: Choose a 'Data Files Location' that has enough space (minimum of (3,609MB)) or free up space on the specified location.
Database configuration failed. Check logs under '/opt/oracle/cfgtoollogs/dbca'.
mkdir: cannot create directory '/opt/oracle/oradata/dbconfig': Permission denied
mv: cannot stat '/opt/oracle/product/18c/dbhomeXE/dbs/spfileXE.ora': No such file or directory
mv: cannot stat '/opt/oracle/product/18c/dbhomeXE/dbs/orapwXE': No such file or directory
mv: cannot move '/opt/oracle/product/18c/dbhomeXE/network/admin/listener.ora' to '/opt/oracle/oradata/dbconfig/XE/': No such file or directory
mv: cannot move '/opt/oracle/product/18c/dbhomeXE/network/admin/tnsnames.ora' to '/opt/oracle/oradata/dbconfig/XE/': No such file or directory
cp: cannot create regular file '/opt/oracle/oradata/dbconfig/XE/': No such file or directory
cp: cannot stat '/opt/oracle/oradata/dbconfig/XE/oratab': No such file or directory

Where is the Data Files Location and where does the restriction of 999MB come from. How can I increase it ? If I leave out -v then the container spins up fine without persisting the data locally of course.

thanks

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