ccms is the abbreviated form for the phrase 'cool,cool,makes sense'. The phrase is used to acknowledge a logical explanation given by another person in a nonchalant manner. Usually, the correct pronunciation demands that you speak the 'c' in an american accent. Sometimes, this phrase is used to fill awkward silences in a conversation.
for example,
software developer: hey, this is the logic to my code.
manager: uhhh...hmm..hmmm...cool,cool,makes sense (CCMS).
software developer: gee, thanks man.