Let me re-phrase that last statement.
If you added 1/4 oz. of hops with an alpha acid % of 12 for 15 minutes to a beer with a gravity of 1.050, it would add approx. 5 ibu's. This could impact the detectable bitterness of your beer, but I'm not that sensitive. However, if the gravity of the beer you are brewing is relatively low, like 1.035, then you may want to consider the potential impact on the final product.