[Plugin: Jetpack by WordPress.com] The Statistics Is Not Accurate

Well, after I installed Jetpack on http://media-islam.or.id, it’s OK for 2-3 days.
Then I saw the post ranking like below. Some of the titles are not appear and there is “(deleted)” word. When I clicked, it went to someone elses sites such as:
http://www.clubpubfail.com/news
http://linkstate.com.br/?p=1522
For the deleted posts:
Hari iniKemarinPekan ini
Judul Kunjungan
Home page 18
Sifat 20 Allah yang Penting dan Wajib Kita Ketahui 10
Doa untuk Ibu Bapak / Orang Tua 7
#14 (deleted) 4
#1522 (deleted) 4
Download Software Hadits Digital Gratis dari Islamasoft 3
#602 (deleted) 3
#632 (deleted) 3
Doa dan Nasehat untuk Mendapat Anak
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I also see significant decrease visitors from 3,322 on March 21 to just 2,037 on March 29.
What happened to Jetpack?
I am afraid spammer had manage to hack JetPack WPStats so the Statistics is no longer accurate.

Please help.

Thank you.

Best regards,
Agus Nizami