I have been observing this for a longtime now, when somebody is speaking with someone he will ask the other one that ''do you understand''? While the person speaking to you is not through with what his saying. So it do confuses me that is why i'm seeking for your opinion to help me out.

It has to do with inferiority complex. They mostly feel their explanation or gist is not being expressed properly so they need your consent before they continue. They’ve done it so long in their life that it becomes second nature. Try and advice them to stop saying it and watch how their confidence in speaking grows when they do.

[UPDATE]
Hmm. Poor guy. I bet he waited for years and didn’t get a reply. I guess my answer came too late. Oh well, at least it’ll help someone else.