Well, in this scenario the image file had 512 bytes sections, each one is called a block. If you have a KiB (a kibibyte = 1024 bytes) it will occupy 2 blocks and so on...
Since this image file had a header with 512 bytes (i.e. a block) I could, in any of the relevant Linux mounting software (e.g. mount, losetup), choose an offset adding to the starting block of a partition. The command would look like this:
sudo mount -o loop,offset=$((header+partition)) img_file /mnt