Data source is SIPRI Arms Transfers Database http://www.sipri.org/databases/armstransfers (the link for the data source is always given below all data visualizations). The latest data available is for the year 2013.

Accoutring to SIPRI exports from Bulgaria in 2013 was US$ 6M, you can check it here http://armstrade.sipri.org/armstrade/page/values.php.

Please keep in mind that figures are expressed in US$ m. at constant (1990) prices.