Unless you are getting a lot of chicks or have a large brooder the big 250 watt bulb may be overkill.
Anyway, the chicks themselves will tell you if they are comfortable or not. It's difficult to accurately measure the level of warmth experienced by the birds when using a radiant heat source (the bulb) so it works better to watch the chicks. This is what you are looking for.
I not only agree with this but give it an A+ it show's exactly what i was talking about were was this thing when i was getting started lol