For this problem, you may need to focus on whether it is "out of scope" (see Article 33 of the Patent Law for details). Specifically, if the original specification and claims do not record the value of 300 or the value range of 300- 1000, there will be a problem that the modification is out of range (beyond the range recorded in the original application).
The patent office strictly examines the issue of out-of-scope revision. If there is such a situation, it will definitely not work and will probably be refuted. If it is within the scope, it can be modified.