fix collectstats argument

Snakefile

@@ -464,7 +464,7 @@ rule collectstats:
     shell: "python {input.colpy} --sample-name {params.sample_name} " \
            "--pre-qc-fastq {input.preqc} --post-qc-fastq {input.postq} " \
            "--mapped-num {input.mnum} --mapped-basenum {input.mbnum} " \
-           "--unique-num {input.unum} --usable-basenum {input.mbnum} " \
+           "--unique-num {input.unum} --usable-basenum {input.ubnum} " \
            "--female-threshold {params.fthresh} {input.cov} > {output}"
 
 rule merge_stats: