I think it's in order of appearance in the series. End Theme was in first episode so that's why it's 4th:
Nevermind, Born Free would have been next to last if that were the case. I don't know why it's 4th.
Full List:
1. Dexter (Main Title) - Rolfe Kent
2. Tonight's the Night - Michael C. Hall
3. Conoci la Paz - Beny Moré,
4. Uruapan Breaks - Kinky
5. Flores Para Ti - Rafael Cortes, , Raw Artistic Soul
6. Blood - Michael C. Hall
7. Con Mi Guaguanco - Ray Armando
8. Perfidia - Mambo All-Stars
9. Sometimes I Wonder - Michael C. Hall
10. Born Free - Andy Williams
11. Dexter (Main Title) - Kinky
12. Escalation
13. Shipyard
14. Deborah Loves Rudy/The House
15. I Can't Kill
16. Voodoo Jailtime
17. New Legs
18. Photo Albums
19. Courting the Night
20. Hide Your Tears