I'm glad you noticed that your answer is too short for IELTS Academic writing task 1. Your IELTS score will be affected if you write less than 150 words for task 1.
The good news is that you may find it easier to write a longer answer in your IELTS test because in the real test the graph, chart, table or diagram will probably contain more information than the graph you summarised here.
If you get a line graph, for example, it will probably contain at least two lines.
To see an example of the type of graph you may have to summarise, check out my blog post 'IELTS Academic writing task 1: what information should you include?'.
To see an example answer, check out my blog post 'IELTS Academic writing task 1: what information should you include? (2)'.