So, bottom line: at 4:30 AM, as Confederates began their 4,000 gun bombardment
Fort Moultrie had three 8-inch Columbiads, two 8-inch howitzers, five 32-pound smoothbores, and four 24-pounders. Outside of Moultrie were five 10-inch mortars, two 32-pounders, two 24-pounders, and a 9-inch Dahlgren smoothbore. The floating battery next to Fort Moultrie had two 42-pounders and two 32-pounders on a raft protected by iron shielding. Fort Johnson on James Island had one 24-pounder and four 10-inch mortars. At Cummings Point on Morris Island, the Confederates had emplaced seven 10-inch mortars, two 42-pounders, an English Blakely rifled cannon, and three 8-inch Columbiads.
That was a grand total of 46 guns.
It's curious that the same Wiki-piece you quote from also reports the following:
"...At 4:30 a.m. on April 12, 1861, Lt. Henry S. Farley, acting upon the command of Capt. George S. James,[26][27] fired a single 10-inch mortar round from Fort Johnson.
"(James had offered the first shot to Roger Pryor, a noted Virginia secessionist, who declined, saying, "I could not fire the first gun of the war.")
"The shell exploded over Fort Sumter as a signal to open the general bombardment from 4003 guns and mortars at Fort Moultrie, Fort Johnson, the floating battery, and Cummings Point.
Under orders from Beauregard, the guns fired in a counterclockwise sequence around the harbor, with 2 minutes between each shot..."
This source says: "The next morning, at 4:30 a.m., Confederate batteries opened fire on Fort Sumter and continued for 34 hours.
The Civil War had begun!"
And that may, finally suggest an explanation here.
Where Wiki says, "4003 guns and mortars", this source says "43 guns in a ring".
If 43 is correct (and it does seem more realistic), then perhaps that figure of 4003 is just a typo, somehow adding zeros where they don't really belong.
It would not be the first mistake uncovered by these Civil War threads.
;-)