What is the best size for a flowchart? How many decisions? (process transactions)

In the process I have to:

*check mails for keywords
*forward mail or not according to the match.

*check mail attachments with keywords
*forward or filter attachments
-If it is an invoice, extract VAT number with regex and make a table.
*Then send these invoices to the correct mail address

now my question is, how many separate flowcharts do you use for this? Or are there any tips on how to keep it organized?

Thank you!