No, you're not cooked. A first practice test isn't a verdict on what you're capable of. It's a measurement of where you're starting before you've actually studied anything, and almost everyone begins well below where they finish. A 495 cold is a completely normal place to start.
Here's what that score does and doesn't tell you. It tells you the size of the climb ahead, which is useful for setting a realistic timeline. What it doesn't do is give you a real diagnostic of your strengths and weaknesses or tell you which topics to prioritize. The sample of questions on a single test is too small for that. So use the 495 to set realistic expectations, not as the study plan itself. The plan comes from the work you do next.
The approach that actually moves a score up from a baseline like this is topic-by-topic learning. Take one area at a time, say number properties, then rates, then a Verbal question type, and learn the concepts and techniques thoroughly. Then practice just that topic, untimed, until your accuracy is consistently high before moving on. For every question you miss, figure out why: was it a concept you hadn't learned, a misread, a careless error, or a trap answer you fell for? That review is what turns practice into progress. Once the content is solid, you layer in timing, and then mixed sets that pull from everything. Speed comes out of mastery. It isn't something you train separately up front.
As for whether the gap is manageable, that depends on your target, which you didn't mention. Most programs sit around 645 and up, so there's real ground to cover from 495. But it's ground people cover all the time with a structured, comprehensive plan and consistent effort. The number you start with matters far less than what you do over the next few months.
If you haven't already, spend a little time getting familiar with the format and question types, then build out a real study plan rather than diving into random practice questions. This article walks through exactly how to start:
How to Start Studying for the GMAT Focus.
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I got 495 in my first GMAT practice exam. Am I cooked?