Hi gildas declercq,
Yes, you can modify the "Data Window Size" by going to the agent in question and clicking the "Configure" gear icon. When the Configure dialogue opens, select "show advanced fileds" and "*Data Window Size" will show up for each module. Note that the setting is module specific and not agent specific.
Note that increasing this value may have unintended side effects like flooding your main collector with data once the agent comes back online, causing delays collecting from the rest of the environment. This is an advanced setting and it is recommended that you proceed with this only if it is absolutely critical for you to do so.