How many more metric tons of coal were produced in 1938 than in 1928

You didn't give us a location or context for this question, but I'm going to guess you might be talking about the ramping up of industrialization in the Soviet Union during the years of Stalin's leadership.  In the USSR, about 100,000 more metric tons of coal were produced in 1938 than had been in 1928.  Stalin (the "man of steel") was eager to make his nation an industrial superpower and be strong for any further war than might be faced.