TTL Flash with Pentax 645

I have had a Pentax 645 for many years, the older, non auto focus camera. I also picked up a Pentax 280AF flash that has the Auto ttl capability.

My question is, is it possible to adjust the power of the auto flash with the cameras +- EV adjustment on the camera body or dose that just adjust the overall exposure with the camera exposure and the flash.

Dose any of the above make any sense?

According to this article it would work for a AF500FTZ flash. I suppose it should work for a 280AF as well.

I assume you mean the AF280T