Number range skip in ARE1

Hai Gurus,

Yesterday we have created an ARE1 and the last official number(ARE1) was 25.Today when i created a new one, there was an error ocurred and Ii couldnt save the document. i tried it few times before finding the solution. When i saved the document, the new number was 30. Here the system skipped 4 numbers. Then I checked in SNUM, but number ranges are not buffered. Could you tell me why did the system skip the number? and what should i do to prevent it from happening again? How can i find the skipped numbers(Same like report RFBNUM00 displays these document number gaps for the number range object RF_BELEG.)

regards and thanks in advance

Gino