Oracle Database Discussions

I am reading oracle online document below

11.3.1 Creating Redo Log Groups

To create a new group of redo log files, use the SQL statement ALTER DATABASE with the ADD LOGFILE clause.

• Run the SQL statement ALTER DATABASE with the ADD LOGFILE clause.

For example, the following statement adds a new group of redo logs to the database:

ALTER DATABASE ADD LOGFILE ('/oracle/dbs/log1c.rdo', '/oracle/dbs/log2c.rdo') SIZE 100M;

My question is for above alter statement, I don't see the group name, then what group it added to...?

Also for the Size 100M in above statement, does it mean the two files in the parentheses each one is 100M, or both files addes together is 100M?

Thanks.