The Chinese economy is worth more than twenty times of what India is, and physically also China is more than six times the size of India. Economically China is at least ten years ahead of India. All said, still China seems to be worried about India. The reason could be the massive stride India has made in the last ten years.
India is also seen as a stronger and dependable partner by US , and there is likely to be a higher rate of US investments into India. That could come at the cost of investments into China. India also has a large pool of talented youngsters who are technology savvy.
Whereas China has a relatively aged population whose contribution would be going down over the coming years. So there is reason behind China’s concerns about India.