why left over oil?

whats up all! quick ? why do some say to save 2ml of oil in syringe to use later? also im new with my one post so just wanted to say great site fellas great info and thanks for the help its much appreciated

I assume its to flush he filter of oil containing hormone.

Your question is very vague and I only posted the above because of the section you chose to post your question.

That's what I was thinking but was t sure thanks for the reply bro I appreciate it just trying to learn as much as I can been in the game a long time just not the make it yourself thing