What is the difference between the editing levels?
When we review a manuscript, we assess it in terms of 'light', 'medium' and 'heavy' editing. Regardless of the level of editing that your manuscript is categorised under, you will still receive the same depth of editing. The only distinction is basically how well the manuscript is written and, therefore, how much work is required to bring it up to the same publication standard, regardless of the state that the manuscript was in to begin with.
For example, if a manuscript is judged as ‘medium’ level, this is because the sample was found to have a lot more editorial errors (e.g. punctuation, spelling, tense, flow, speech etc) than if a manuscript is judged as ‘light’ level.
The reason the editorial team review a sample of a manuscript to judge the level of editing required, rather than just blindly quoting for the amount of editing based on word count, is because every manuscript and author are different and should be treated as such. It, therefore, wouldn't be fair to charge authors who have light level manuscripts, the same price for editing as a manuscript that required heavy editing.