Dear....
You have asked for justification as to why I should get a pay rise salary arrangements.
Here are the reasons:
(List the reasons, presented as 3-7 concise clear bullet points. Where you attach values show them rounded to nearest 100 or 1,000 or 5,000 depending on scale, or shorten using the k symbol, eg $50,000 looks tidier when shown as $50k) in a column ranged right margin one above the other, and you can even show a total value bottom right if appropriate - see the examples of reasons below, and tailor to reflect your own situation).
(Then add) I'm happy to provide more detail on any of the above if you need it.
(End with something positive like) I thank you for this opportunity to present this information. I greatly enjoy working with the company, I am pleased to give my loyalty and commitment, and to take on extra work and responsibility. I am keen to be trained, to progress, to learn new things, and I want to contribute as much as possible to the company's success in the future.
I look forward to your response.
Yours