There are 2 entries for each transaction. 

Therefore, if your company has an example of 10 invoices per month, then 10 × 2 is 20 entries.

Also, entries are payroll, inventory change, and so on.

There are 4 entries for each transaction with VAT. 

VAT payers add 2 entries for each sale and purchase transaction.

Therefore, each mentioned transaction means at least 4 entries for a taxable person, in some specific cases even more.

The VAT is not included in payroll etc.

The general VAT rate is 20%, but it also depends on the service/product sold and the customer’s type (B2B vs B2C) and location (Estonia, EU, outside EU).