Partition #3 contains a ext4 signature

When i use fdisk to create a new partition i get an error which says

Partition #3 contains a ext4 signature

Do you want to remove the signature? [Y]es/[N]o:

This error is not a problem but i am wondering why this error even comes up when the partition has not even been created with a filesystem. While creating a partition i only had two partitions which were #1 and #2, there was no third partition at all. So how is there already a signature of a ext4 filesystem on the partition?