The first template to choose is the Detail, and this should be for the line that occurs most frequently. So here, the Deposits, I guess, will be the most frequent line, so make those the detail, then the rest are Appends if they appear above the Detail, or Footers if below.
You need a special type of Append called a Page Header only if you have a multi-line Detail that is split over page breaks. The limit, by the way, is about 22 templates in total, but only ever one Detail. If you start processing really gnarly XML files then you might begin to get close to the limit, but for an account statement in plain text I don't think you should worry.
Hope this helps,
Jeff, just to add a little to Olly's response ...
A typical report with some obvious detail might have a list of transactions for an account - depositis and withdrawals - that would most likely be considered to be the detail lines.
There will likely then be some general information about the account above the details lines (rarely but not unheard of that could be below the details) and probably above that some information about the customer (who may have several accounts). It is possible, though perhaps unusual, for an account to have several "customers". In that case the order may be reversed. Either way Account and Customer would usually be Appends in Monarch terminology with each Append being connected to one or more detail lines. Appends, as mentioned above, USUALLY are presented ABOVE the details lines of a report but there can be some exceptions related to individual analysis needs and there are ways to address that situation in Monarch should the need arise.
FOOTERS are used for data lines that appear AFTER the detail lines, most typically for summary details - Total transactions and that sort of thing. Thinking of the structure suggested above they may be subtotals for a detail transaction type (Deposits, withdrawals), an account or a customer - or indeed one for each of those. Or perhaps (less usefully in most cases) a subtotal for a section of the report or a total for the entire report. Footers might also be used for other things so long as they appear at a point that is useful for the analysis required - perhaps a collection of notes about a customer providing the notes can be linked by footer to only the intended customer.
If you can visualise the structure of a report it is a great help when deciding how to model it. Some reports may not have a visually obvious structure and can take more time to analyse before you can properly "see" the structure of the contents you need to work with and map them to the combination of detail/append/footer templates you will need to deploy.