Why  153  Fish  in  John  21:11  ?

of the Four Gospels written in the language of Old Church Slavonic.

The script is called Glagolitic font.

The color code below identifies the key words.

The letter " Ižɛ" was used for "+" between the numbers spelled out

so that the pink words meant 100 + 50 + 3 

Below is a second image

The yellow line indicates where verse 12 begins.  The last two "red" letters transliterated into Latin

are  "IS." 

This is as an abbreviation for Jesus. 

In the Latin Vulgate, the name of Jesus is rendered as "Iesus" 

Portrait format

Landscape format

Above image adapted from Omniglot

The Glagolitic letters are Green, (Two of those were changed to purple for easier identification.)

Directly beneath each letter are two lists of the name of that letter. The first is written in Glagolitic letters.

The I was changed to red show the close relationship with the letter before it, the  Ižɛ

The Cyrillic equivalent letters are in Blue, and

the Latin equivalent letters are in Red