Why is the string split when outputting ASCII strings in MBR?

Question

In the MBR program, the following code is used to print "Hello world" to the screen:

section MBR vstart=0x7C00
    mov sp, $$
    ...
    ; Set the memory address of the graphics card to the ES register.
    mov ax, 0xB800
    mov es, ax

    ...

    ; Output string to 0xB8000
    mov byte [es: 0x00], 'H'
    mov byte [es: 0x02], 'e'
    mov byte [es: 0x04], 'l'
    mov byte [es: 0x06], 'l'
    mov byte [es: 0x08], 'o'
    mov byte [es: 0x10], ' '
    mov byte [es: 0x12], 'w'
    mov byte [es: 0x14], 'o'
    mov byte [es: 0x16], 'r'
    mov byte [es: 0x18], 'l'
    mov byte [es: 0x20], 'd'

    mov byte [es: 0x01], STYLE
    mov byte [es: 0x03], STYLE
    ...
    mov byte [es: 0x19], STYLE
    mov byte [es: 0x21], STYLE

    jmp $

; Set the style of the string, the background color is green, the text is blinking, and the foreground color is black.
STYLE equ 0xA4
times 510-($-$$) db 0
db 0x55, 0xAA

I get this result:

It looks like a break in groups of 5 characters. why is that?