630 or 645pm is the last two donor slots. So you must make a appointment before than. In addition. If you try to make a appointment at the last minute, all available slots could be taken and you won't be able to schedule at those times. It's possible to show up at the last minute and they could let you donate if it's in time if enough cancellations occur and such luck shines in you.
I believe its 7pm
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