The shown charging wattage is correct. The whole wattage of the MagSafe is divided into charging the battery and running your Mac. So probably your Mac needs ~35 W and the rest of ~50 W is used to charge the battery.
You may estimate the needed wattage of your Mac by temporarily unplugging the MagSafe.
The power usage (and the realtime Usage in mAh) provided by the battery will change to certain amounts. After replugging the charger this will change back to the charging wattage.
On my MacBook Pro I get the following:
On Battery: ~70 W (- 6510 mAh)
Charging: ~6 W ( - )
Estimated total wattage: ~76 W (not taking into account that the power consumption is slightly lowered in battery mode)
After quitting a power consuming app running in the first attempt I get
On Battery: ~40 W (- 3980 mAh)
Charging: ~32 W ( - )
Estimated total wattage: ~72 W