hi,
The delay is nothing but the buffer time. If you go through wowza User guide chapter 5 (Advance configuration Topics) you will see the following details:
For HTTP Streamers such as Cupertino (Apple HLS), Smooth (Microsoft Smooth Streaming), and San Jose (Adobe HDS), the on-demand startup model doesn’t work. An iOS device requires about 30 seconds of video to be pre-packetized before it can begin playback. Microsoft Silverlight clients require three times the key frame duration. Therefore, it’s necessary to start the stream prior to the stream being ready for streaming to these player technologies
Hope it helps to clear your doubts
regards
Jason