You can't. Timecode can't go below zero.
Instead of making the movie start at 0 you can let it start at 1 hour if that is not a problem
Start Time would be: 00.00.49.00.
Should not make a jot of difference to the audio engineer what TC the Program starts at but ask him why maybe.
Generally we use 00:01:30:00 for Program Start and the SMPTE leader precedes this if we use one at all. ( More out of habit than neccesity)
FWIW: Countdown Leaders dont play as big a part in digital media as much as they did in analogue and tape deck days.
It is standard procedure to have the first frame of action start at hour 1 (01:00:00:00) This helps the post production folks especially when passing an OMF which may contain items that happen before the first frame of the film (IE if you start your film at 00:00:00:00 and you put an Academy/SMPTE leader in front of it, the leader will occur in negative timecode and the software will quite often have trouble figuring out where to place it). I've have to assume that shooternz does not pass audio to post houses for work. The Universal Leader/countdown provides the starting sync pop (2-pop) with matching flash frame 2 seconds prior to the start of the film. Who ever heard of a film starting at 00:01:30:00 It's best to stick to standards (that's why they're standards!)