It is 4 because the image size is greater than 2.88 MB
The number of loaded sectors specifies the number of 512-byte sectors to be loaded from the boot image.
1 specifies a 1.2 MB floppy disk image (512-byte boot image),
2 specifies a 1.44 MB floppy disk image (1024-byte boot image),
3 specifies a 2.88 MB floppy disk image (a 1536-byte boot image),
4 specifies a hard disk drive image (a 2048-byte boot image).