Your role is to comment on the usage of English during the meeting, and to count how many times speakers use filler words such as “ah”, “um”, etc.
Before the meeting, prepare to explain the purpose of your role and how you will do it (for example what you will be concentrating on). You could mention that it is better to speak slower and to pause to gather one’s thoughts than to use filler words, for example.
Tip: It is useful to point out outstanding use of English, as well as incorrect English. For example, you might compliment speakers on their use of very descriptive words, or for their success in explaining a complicated concept in everyday English.