InnoDB extends the data file if it runs out of free space in the tablespace. The increment is 8MB at a time by default. In your example actual data file size is less than 60G. If you want to know how much free space is available in this file then run this command on any innodb table.
SHOW TABLE STATUS LIKE 'table-name';
and look for "Comment" field that will tell you how about innodb free space.
if your hard disk gets full then Innodb wont be able to extend this data file. If this happens then you have following options
1. Add another physical disk; Edit your my.cnf file to add 2nd file data file.
[mysqld]
..
innodb_data_home_dir =
innodb_data_file_path = /path/to/current_data_file/ibdata1:10M:autoextend;/drive2/ibdata/ibdata2:2000M:autoextend
Restart the server.
http://dev.mysql.com/doc/refman/5.0/en/innodb-configuration.html
2. Shrink some of the tables ( if possible)
3. Alternatively if you want to shrink ibdata1 file then
1) You would have to enable innodb_file_per_table. Restart mysql server
2) Backup your database.
3) Stop mysql server
4) delete ibdata file
5) restore database from backup