How to decrease counter without using counter-reset

I've searched for this but I couldn't find anything similar to my problem.

Basically what I have is a counter called page and I'm setting up a page counter like this:

content: "Page " counter(page); that is displayed like this on screen -> Page 1

Everything is working fine, but what I need is to set the page counter to start from 0 instead of 1

I'm using a Wiki (confluence) and I don't have access to where page is defined, because it's just a variable meant to be used for CSS counters like before.

I tried to following, but with no luck at all:

content: "Page " counter(page) - 1;

content: "Page " counter(page - 1);

content: "Page " calc(counter(page) - 1);

I've also tried to prepend counter-reset:

counter-reset: page -1;
content: "Page " counter(page);

Now my question is, can I set the counter to start from 0 without using any counter-reset property? Or, in the previous example where I actually tried to use the counter-reset, did I make any mistake? Am I missing something?

Solution

If you have landed on this page looking for help on usage of CSS counters with the confluence tool, please make note of the comment by Nick:

I wrote a thread in confluence support forum, but apparently what I want to do it's not possible.

Here is one way to make it start from 0 without using counter-reset: [counter-name] -1. Basically what we are doing is incrementing the counter only from the second occurrence of the div class='page' so that the counter value for the first instance always remains 0.

counter-reset does not seem to be a mandatory property^*. When there is no reset mentioned, 0 is taken as the default value and the below code still works.

^{* - Can't find any reference in W3 docs or in MDN that counter-reset is optional but browsers seem to support it.}

body {
  counter-reset: page;
}
.page:before {
  content: "Page " counter(page);
}
.page ~ .page {
  counter-increment: page;
}

<div class="page"></div>
<div class="page"></div>
<div class="page"></div>
<div class="page"></div>

I have posted the above only for a sample and I don't think it is the correct way to do it. The recommended approach would be the below where while resetting the counter, we set the start value as -1.

body {
  counter-reset: page -1;
}
.page {
  counter-increment: page;
}
.page:before {
  content: "Page " counter(page);
}

<div class="page"></div>
<div class="page"></div>
<div class="page"></div>
<div class="page"></div>