reported bloom filter FP ratio

[Radim Kolar]

I have following CF

                Read Count: 68844
                Read Latency: 9.942 ms.
                Write Count: 209712
                Write Latency: 0.297 ms.
                Pending Tasks: 0
                Bloom Filter False Postives: 10
                Bloom Filter False Ratio: 0.00495
                Bloom Filter Space Used: 2196632

why reported bloom filter FP ratio is not counted like this
>>> 10/68844.0
0.00014525594096798558