"Notify without deletion" is more in the vein of "you're wrong, but we're going to let you off lightly," i.e. it's not a severe violation of the rules.
Your account is too new to delete posts - that only happens after a while, 3 days of visiting the boards as you said.*
Personally, I just wouldn't worry about it. Sure, you slipped up, but now you know better - just try not to make the mistake in the future and everything will be fine. (And I guess if you're really worried about it just delete the post in a few days when you get those privileges.)
* - Technically, Provisional accounts like yours CAN delete new posts under certain circumstances. Depending on your email provider, your account is assigned to one of several different Provisional tiers on its creation - your account landed in one of the ones that won't be able to delete posts, however, and you'll have to wait out the three days. After the few days everyone's account is essentially the same and email provider doesn't matter anymore.
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