Sorry - that's not a phrase I recognise. It would only have a literal meaning - how many words did you say? Did you possibly mean 'Can I count on your words'? But even that is a little unnatural. There are many expressions: 'Are you on the level?', 'Are you for real?', 'Can I count on that?', 'No kidding?', 'truly?',...

Actually this is my first time I heard this sentence, maybe it means that, sounds like 'Are you serious?', 'You joking?', 'Really?'

I believe I have read the phrase "Can I count on your word?" before. But it does seem rather unnatural, if not eccentric. If you want something similar I presume you would have to go with "I will take your word for it"