Access 2000-auto fills data

I’m trying to find out why Access 2000 will auto fill my data entries. I’ve noticed that after I enter a number in a field that in the next record, in that same field, the next number is automatically inserted in that field. For example, in my Order column, in datasheet view, I enter a 1, the next record in the the Order column will automatically fill with a 2 and so on. Or the pattern will repeat – if I enter a 1 in the Order field, then a 3 in the next Order field, the next Order field will fill with a 5. What is going on? and how do I stop this?