Yes, the percentage is indeed the tolerance. A 5% resistor has better tolerance than a 10% which only means it will be closer to the claimed value of the resistor (27 ohms in this case).
I second what the others have said, these really should be replaced with resistors with a higher power rating, like the 5W devices timerider linked.
Your other (better) options is to replace the bipolar power transistors in the lamp matrix with MOSFETS. instructions are in the thread budwin linked. This GREATLY reduces the heat generated by the lamp matrix reducing backbox temps extending the life of the boards and backglass.