Most of it. They knew that Lincoln was sending ships. They knew that Lincoln told Pickens that the intent was to land food and supplies only, and no men or munitions would be landed unless opposed. They knew the ships were loading in New York. They knew that Davis had ordered that the resupply be halted regardless of the consequences. That's all detailed in "Allegiance" by David Detzer. A book that I have read.
So, you would agree it was a fact that the residents of Charleston were correct in their knowledge that a Union fleet was arriving, and that they had stated their intent to enter the harbor, by force if necessary.