Did you read my post above? 303 has a hatnote to 303 (disambiguation) which links the Roland TB-303, so there is no need for a hatnote at top of 300 (number). Imagine what a humongous hatnote we could get if we started duplicating everything at pages like 302 (disambiguation), 303 (disambiguation), 304 (disambiguation), 305 (disambiguation), 306 (disambiguation), 307 (disambiguation), 308 (disambiguation), 310 (disambiguation), 312 (disambiguation), 314 (disambiguation), 316 (disambiguation), 322 (disambiguation), 323 (disambiguation), 336 (disambiguation), 380 (disambiguation). None of these have a corresponding "3xx (number)" article. You are free to create a new article at 303 (number). See Help:Redirect#Creating and editing redirects.