The title is talking about the magnitude of the explosion, not the quantity of explosives. It's just coincidence that the numbers 275 are in both the weight and magnitude.
From what I read, the blast triggered a shockwave that would measure between 3.5 and 4.5 on the Richter scale. Charts that I saw would place the explosion around 3 to 5 kilotons, so the title is accurate.
a former British Army bomb disposal expert says the Beirut blast was the equivalent of 1-2 kilotons of TNT
I'll have to try and dig up and see if I can find the link that was saying 3-5, but not sure if I saved it. I think what I saw was just estimating based on the Richter scale where a 5 kiloton nuclear bomb caused a 4.5 quake to register, so they were estimating based on the seismological data and previous explosions
It was previously reported that 2,750 tons of ammonium nitrate was stored at the harbour. I am marking this as misleading title.