the most populated country in the world
This is not a part of the image presentation so the reference to China's actual population is not required and will not be given a scoring consideration.
with a considerable gap
A considerable gap in relation to? This is a confusing statement. This aspect of the sentence could have been omitted without affecting the clarity of the sentence idea. It's inclusion led to a problem in understanding your sentence topic reference.
there were more than 700 million Chinese
Where actual numerical data is given, use the actual data. You will receive deductions for misrepresenting table data in this case. Implied information can only be used when dealing with line graphs that do not actually hit a specific figure in the presentation.
In relation to? Look, there were 10 countries referenced, all with their own information covering 3 aspects. The presentation should have used 2 grouping presentations that properly refer to the internet users, percentage of population using the internet, and the total population. You cannot use selective information presentation in a task 1 essay because specific information is presented for your analysis and reporting output.