The essential requirements of a court/tribunal bundle are that each page should be numbered and there should be an "index" (i.e. table of contents) at the front giving the date and description of each document and its page number.
The page numbers are essential so that everyone at the hearing - judge, witnesses, and counsel - can be sure they are looking at the same page. For example, a barrister may say to a witness "please open volume B in front of you, and turn to page 562" and then ask the witness a question about the document at page 562. The page number enables the judge and the other barristers to also turn to the same page in their copies of the bundle.
It can take a witness a little time to find page 562. Most people, when looking for a page number will open the volume where they guess the page number might be. That might turn out to be, say, page 403. They will then estimate what thickness of pages to turn over, ending up at, say, page 539, and so on, until they are near the page number they are seeking when they will probably start to turn over a page or a couple of pages at a time until page 562 is reached. This is done instinctively but it can take a little time and make it more difficult for witnesses to concentrate on the question they are being asked.
To assist everyone, it is very useful if numbered dividers are placed at intervals in the bundle. Numbered dividers can be bought from any stationery shop and look like this.
If the bundle has numbered dividers, the barrister can say to a witness: "please open bundle B in front of you, go to tab 62 and turn to page 562". This the witness should be able to do quite quickly.
It is, of course, essential that the numbered dividers are inserted in exactly the same position in every copy of the bundle - e.g. if tab 62 is immediately before page 549 in the copy of the bundle in the witness box, then tab 62 must be immediately before page 549 in all other copies of the bundle - i.e. the copies used by the judge and by counsel.
As a guide, tabs should be inserted every 25 pages but it does not have to be exactly every 25 pages and you should not insert a tab in the middle of a document. The most important thing is that all copies of the bundle should have the same number tab before exactly the same page.
If the Index at the front of the bundle lists tab numbers as well as page numbers, so much the better, but it is still worthwhile inserting numbered tabs even if the index only contains page numbers.