the percentage represents how likely the eclipse code recommenders (archived project since july 2019) think it is that you are looking for a certain completion based on the context and maybe prior usage and other variables (there are "5 intelligent code completion engines"). it is not only the bare usage statistics. so a value might change from 13% to 95% between some lines, depending what you did in between.

see the docs for details (archived project since july 2019):

it assists developers by recommending him only those methods that are actually relevant for his task at hand. for instance, given that a developer just created a text widget makes it obvious for code recommenders which methods a developer wants to use next - even if the developer doesn't know it by himself.

a download of the now archived project can be found here:

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