It looks as though you are calculating in avoirdupois weights. Gold is measured in troy weight. 275 troy pounds is about 225 avoirdupois pounds, or just over 100 kilograms. The volume of the gold would be a bit more than 5 liters, or about 310 cubic inches, so a 9X9 ingot would be not quite 4” thick.
Pardon the imprecision, but I don’t have a calculator handy, so the numbers are in-the-head estimates.
Going at a different way, the article quotes the value of the gold at $4.8m. Gold right now is running around $1200 per troy ounce. So, that's 4000 troy ounces, or 4389 regular ounces, or 274 regular pounds, or 333 troy pounds, there being 12 troy ounces per troy pound.
The next part of the calculation is volume. 4389 avoirdupois ounces is 124426 grams. Dividing by gold's density 19.3g/cc, we get 6447 cc of gold, or 393.4 cubic inches. So, if two of the ingot's dimensions are 9", then the third is 393.4/81 = 4.86".
Pardon the imprecision, but I don’t have a calculator handy, so the numbers are in-the-head estimates.
I just use Google. It recognizes expressions and unit conversions and gives the answers up top. E.g., type in 4000 troy ounces in pounds, and back comes the answer 274.285714 pounds.