Change Request Documents Number Range

Dear All,

For the transaction type SDCR & SDHF i have maintained Internal number range & un tick the early no assignment option. For few days there was no problem, but when i seen today, few numbers were missing for both CR & UC. When i checked in SNRO / SNUM the buffer maintained is 10. I dont want this skipping of CR & UC numbers in between. Hiow can i restrict this ? If i made buffer as 0, is there any issue will create ?

regds,

CB