You gain 2 life. Target creature gets +X/+X until end of turn, where X is the amount of life you gained this turn.
Fortifying Draught counts the total amount of life gained without considering any life you lost during that turn. For example, if you lost 2 life and gained 3 life earlier in the turn, you will gain 2 more life from Fortifying Draught and the target creature will get +5/+5.
