During the creation of an AUDIO CD, files are separated into tracks, which results in larger file size. An AUDIO CD holds about 15-16 tracks depending on their size.
If we calculate 275MB/4MB (average track size) = ~69 tracks. You will need 4+ CDs to burn all the tracks (calculated at 16 tracks/CD).
Try to create a DATA CD instead of AUDIO CD to be able to burn all the 275 MB of data.