My name on passport is my first name is XXXX YYYY and Last name ZZZZ. However, in GRE registration my first name is XXXXYYYY (no spacing) and last name is okay. I called GRE helpline and they said it won't be a problem.
On the website it says:
The name you use when you register — and the spelling of that name — must exactly match (excluding accents, apostrophes and spaces) the name printed on the identification (ID) documents that you will present on the day of the test. If it does not, you may be prohibited from taking the test or your test scores may be canceled after you take the test.
I think it won't be a problem but I am still worried.
When I apply for graduate programs, would it be a problem?