The program wodim has been created by a group of OSS-hostile people in May 2004 with the intention to fool users. wodim did not get fixes since August 2004 even though there are plenty of bug-reports against that specific variant of the software, so do not use it.
You better use the original software cdrtools and the program cdrecord and you should know that is is unwise to call cdrecord with arguments like dev=/dev/sr0 in special when you are on Linux since Linux implements several competing drivers of different quality for the same hardware that are available at the same time and dev=/dev/sr0 typically enforces to use the worst of the existing drivers. If you use the officially documented syntax for dev=, cdrecord is able to automatically select the best driver available instead and if you only have one optical drive in your machine, cdrecord even automatically discovers the right interface by it's own if you ommit dev= completely.
For your wishes, the best way to go is to call:
cdrecord -minfo
as this lists all tracks and all related sessions and their numbers. You may need to experiment in order to find out whether your OS has an offset-by-one problem with the session number with the mount option.
Note that the option -minfo has been added in November 2006, so you need a cdrecord version that is recent enough... Some unfriendly Linux distros may not have updated their software since then. Gentoo, Arch, Suse, ... are some friendly Linux distros with up-to-date software.
It may be of interest that the original software more than doubled it's source code and it's feature set since 2004, when the OSS hostile people created the fork you are using.
If your distro is one of the unfriendly distros, get the recent source in schilytools from http://sourceforge.net/projects/schilytools/files/ and compile it by just calling make.
Let me add parts from a typical output from a mult-session CD as seen in the net as a result from a cdrecord -minfo -v call:
ATIP start of lead out: 359847 (79:59/72)
...
Track Sess Type Start Addr End Addr Size
==============================================
1 1 Data 0 299 300 -1
2 2 Data 11702 21333 9632 11402
3 3 Data 28236 78091 49856 6902
4 4 Blank 84994 359844 274851 6902
Last session start address: 28236
Last session leadout start address: 78092
Next writable address: 84994
Remaining writable size: 274851
BTW: the last colum without header is the size of the lead out area after the recorded data. The first lead out size is 11402 sectors, the size of the other lead out areas is of the reduced size 6902 sectors.
In this case, there are 3 written session on the disk. The 4th session mentioned in the list is the remaining free space on the medium.
Finally, let me add a comment on the baseless claims frequently seen against the original cdrtools, where people assert that cdrtools allegdly have a license problem. The legal department fom Sun Microsystems, Oracle and SUSE as well as Eben Moglen all made an in depth analysis and confirmed that there never has been any license problem with the original cdrtools.
