对 count(*)结果进行 sum 操作为啥会有小数

需求是对 SPBM 、SPMC 分组，计算 ZJ/CKSL 最小值及其条数，最大值及其条数， 使用的数据库 Oracle 。

SELECT SPBM,SPMC,  round( MIN(DJ),5) AS MIN_DJ, sum(CASE WHEN min_rn = 1 THEN sl ELSE 0 END) AS MIN_SL, round( MAX(DJ),5) AS MAX_DJ, sum(CASE WHEN max_rn = 1 THEN sl ELSE 0 END) AS MAX_SL from 
(
  SELECT SPBM, SPMC, ZJ/CKSL as DJ , count(*) as sl,
         ROW_NUMBER() OVER (PARTITION BY SPBM,SPMC  ORDER BY ZJ/CKSL  ASC) AS min_rn,
         ROW_NUMBER() OVER (PARTITION BY SPBM,SPMC ORDER BY ZJ/CKSL  DESC) AS max_rn
  FROM SP 
  GROUP BY SPBM, SPMC,ZJ/CKSL  
  )
 WHERE min_rn = 1 OR max_rn = 1 
GROUP BY SPBM,SPMC

从运维导出的结果 excel 里发现 MIN_SL,MAX_SL 这两个数量存在小数，不知道为啥？