What result is that? Is it a TSH level? A TSH of 0.28 is quite low... TSH is counter-intuitive; when it's high, thyroid hormone levels are, typically, too low and when it's low, thyroid hormone levels are, typically, too high... the latter is the case with Graves Disease: low TSH/high thyroid hormones.
Is that the only test you've had done? What about Free T4 and Free T3? It's very rare to gain weight with Graves Disease, though not impossible.