Cantrip: Blade ward: how much resistance to melee attack?
In D&D resistance means that damage of a specified type (or types) is halved.
If you cast Blade Ward on yourself and get attacked for 5 slashing damage. Blade Ward would lower that damage to 3. (5 / 2 = 2.5, rounded up => 3).
But your point still stands. Perhaps they should add a tooltip on hovering over the 'resistance' word that would explain this.