Agreed, it does beg the question. Three digits of precision does not mean there isn't an error of +- 100 tonnes on the actual source calculation. I can imagine

Agreed, it does beg the question. Three digits of precision does not mean there isn't an error of +- 100 tonnes on the actual source calculation. I can imagine an engineer in the FBI did some modeling using damage radius, height of blast, etc. to get a rough estimate. News, being news, cuts off the error or the FBI, trying to look very competent, omits the error.