So, the current plan for the BFR has the spaceship massing 85 tons and carrying 50 tons of cargo plus around 1000 tons of fuel and oxidiser (according to wikipedia), most of which is presumably expended getting into orbit. Then, for deep space missions, the spaceship is supposed to be refueled by the BFR tanker. This is usually shown on the animations etc. as just one tanker flight per spaceship, but the numbers don't seem to add up. Even if the dry mass of the tanker is less, say 30 tons, it will only deliver about 100 tons of fuel/oxidiser to LEO, so it looks like it would take about 10 tanker flights to fully refuel the spaceship.
Does anyone know if that is actually the plan? or have I miscalculated somewhere? or does the spaceship not need to be fully refueled for (say) a Mars mission?