The RAF dropped 2,659.3 tons on the city and the USAAF dropped 782 and then 465.6 tons on the marshalling yards, as the chart shows.
That total for the 13th-15 of February is 3,906.9 tons dropped. That’s where the 3900 ton figure comes from in the part you picked to copy and paste.
http://en.wikipedia.org/wiki/Bombing_of_Dresden_in_World_War_II#Timeline
All US airstrikes were on the marshalling yards and industrial areas.
http://www.history.com/this-day-in-history/firebombing-of-dresden
http://www.historylearningsite.co.uk/bombing_of_dresden.htm
We are never going to agree on this, but have a good day and a great life.