What Bog means is that if you would normally bet $1.5 on that pot, bet $1.5 + 0.45x2 for $2.40.
A quick way to calculate a pot-sized raise (making the villain call a pot sized amount) is double their bet plus the pot. In this case 2x 45c + 1.80 for $2.70 would leave the villain having to call an extra $2.25, and the pot + his original bet is $2.25
Pot size is normally a bit big for protecting but it gives you a guideline. $2.70 is a full pot call for the villain so you can bet say $2.2 and be protecting at about 2/3.