The desk and chair were shaking a little heavily when I was tutoring a middle school student at about 16:23. After a while, about a minute, it stopped. My wife called me and told me that The magnitude of this aftershock is 6.4 which happened in Qingchuan, Sichuan, heard from TV.
The date from China Earthquake Networks Center:
地震参数 时间: 2008-05-25 16:21:47.0
纬度: 32.6
经度: 105.4
深度: 33
震级: Ms6.4
震中位置: 四川青川
受影响地区 包括震中50km范围内的县城和200km范围内的大中城市。(括号内为方位角)
震中位于：
青川县东16km(82°)
http://www.csndmc.ac.cn/newweb/secondpage.jsp?id=751
However, the EMSC said it was 5.9.
The data from EMSC:
Magnitude mb 5.9
Region: SICHUAN-GANSU BORDER REG, CHINADate time: 2008-05-25 at 08:21:49.0 UTC
Location: 32.62 N ; 105.45 E
Depth : 10 km
Distances : 45 km NW Guangyuan (pop 213,365 ; local time 16:21 2008-05-25)
125 km NW Baoning (pop 60,542 ; local time 16:21 2008-05-25)
http://www.emsc-csem.org/index.php?page=current&sub=detail&id=87194