Weird union rule regarding seniority

So a coworker and I both want an earlier shift. We started the same day, so per the union contract, it goes by last four of rn license #, whoever is lower. She wins per that rule even though I have 3x as much experience. However it says in the contract if still not resolved, then it goes via the whole RN license #, whoever is lower That would mean I would get it because my # is much lower than hers. So per the union interpretation she gets it because it would be "resolved." Meaning I can't challenge it. I don't think they're interpreting it right. I think the goal is to hope the more experienced person should be able to challenge it because ultimately the Lower # would normally indicate more experience.
Just curious on others thoughts regarding this. It just seems like an odd method to determine the seniority. Why not just base it on something like RN experience in years?
If you go by their "rules" then experience is complete discounted and not rewarded. Management agreed to me challenging it and gave it to me as I think they interpreted it same way I did. However, union could apparently fight it per union rep if she chose to fight it.
I am not looking for advice, just seeing if others out there have had similar odd rules for determining seniority. I'm debating discussing this with the union to see about altering it in future contracts.
Seniority with a position should count for something as well- it shows a loyalty to the employer, and why shouldn't that be rewarded? I'm not a union facility, but seniority is how we work out a lot of similar things (vacation requests during "prime time", changing shifts, etc). Yes, last 4 of a nursing license seems kind of random, but then again, how often does it need to get used? Your situation is probably as likely as holding a winning lottery ticket- extremely rare.

I agree that seniority should originally be based on whoever has been there longer. This wouldn't be an issue in that case. I just would have though experience would be the next factor. 6 years versus 1 1/2 years experience. However that is not the case.I think they meant for that to be the case, but the way they wrote it isn't very clear and basically it turns into a lottery. . This will be a more common issue though because they hired about 15 nurses in groups with several of the same start date each day, it will be something they will continue to need to address. It is what it is but at this point neither of us are likely getting it. So we will continue to both keep striving for an earlier shift. At this point we may as well be arm wrestling for it.

I've been on the short end of some silly tie-breaking decisions. All I can add is to say 'what would have been your take on the situation IF you had been the WINNER of the lottery'?The union needs to re-evaluate its policy and develop something new. Might you and others petition them to look into the process?

I agree with using the entire nursing license number, and with what amoLucia said. This rule needs clarification. And going forward, HR should start time-date stamping employment applications. Reward the nurse who got there 10 minutes after the office opened in the morning, versus the nurse who straggled in at 3:30 pm!

I have saved the policy and am going to ask for clarification. I honestly would have expected experience to always be the tie breaker, regardless of if I'm the one with more or not. Basing it on the last four could make the difference between a nurse of 10 years experience and a new grad and the new grad scoring jt. If she had had more experience I would definitely expect her to get it. After talking with other staff regarding a hypothetical all across the board agreed the first part of the tie breaker should be removed and it should be the entire license number always. Thanks for your thoughts and I will be presenting it to the union.