I am planning to install about 17,000 sq.ft. of the new TifBlair centipede seed in May or June in an expanded lawn area. I have just applied CGM granules at a rate of about 20 lb / 1000 sq.ft to kill off the weeds before planting. The planting instructions for the seed say to fertilize with 5-10-15 fertilizer at a rate of 10 lbs. per 1000 sq. ft. before seeding.

During the growing season, centipede does not need much nitrogen, if any. It enjoys a boost with iron, however.

What is the equivalent organic fertilizer to apply pre-planting?

Ignore that npk recommendation. CGM is a good start. Lava sand and greensand next would be good. I would also take a look at the cost of a thin application of a quality compost. The greensand will give you the needed iron.