To optimize the space in the CD-r or DVD-r we can burn it more than once. It's called multisession disc. For this action we need a help from third-party program. In this tutorial I use Nero.
Here it is:
1. Open Nero Program
2. Choose Make Data Disc
3. Then choose folders and files that you want to written to disc.
4. In the Final Burn Settings Window choose Allow files to be added later (multisession disc).
5. Click Burn
Now your CDs or DVDs can be burn more than once.