I converted to US measure to check my figures -- if all strawberries are used, you've got 5.85 lbs per US gallon, which is @BigDaveK's figure. 14 kg is spot on for the volume.
Also keep in mind that a "recipe" for a wine is not absolute. It's not like baking a cake or bread where the ratios of ingredients IS important. If a wine "recipe" says 4 to 6 pounds of fruit I would venture to the upper limit or more.