“Partial solution” on Code Eval for Clojure FizzBuzz

Question

I'm just getting started on the site CodeEval, and I submitted my first solution today. What I don't understand is why it's marking my (working) answer as only a "partial solution". The site doesn't seem to want to explain why my answer is only "partial", and I'm hoping someone here can explain why.

The challenge I was trying to do was FizzBuzz, where you take in three numbers as input and output a sequence of increasing numbers, substituting "F" for a number if it's divisible by the first input number, "B" for a number if it's divisible by the second input number, and "FB" if it's divisible by both.

Here's my solution:

(defn process-line [[x y n]]
  (for [i (range 1 (inc n))]
(cond

  (and (zero? (mod i x)) (zero? (mod i y))) "FB"
  (zero? (mod i x)) "F"
  (zero? (mod i y)) "B"

  :else (str i))))

(defn string->int [string]
  (let [elements (clojure.string/split string #" ")]
    (into [] (map read-string elements))))

; Sample code to read in test cases:
; Open the file passed as the first command line argument
(with-open [rdr (clojure.java.io/reader (first *command-line-args*))]
  ; Read each line ignoring empty ones
  (doseq [line (remove empty? (line-seq rdr))]
    (let [out-line (process-line (string->int  line))]
    (println (clojure.string/join " " out-line)))))

The only thing I can think of is the following: when it shows the memory usage of my working solution (it currently uses 71098368 bytes) there's a little tooltip that says "Reduce memory usage to 20Mb". Is that the cause of the "partial" in my solution, and, if so, how could I reduce my memory usage? My solution already seems pretty simple.