[Plugin: Image Gallery with Slideshow] Thumbnail width and height setting issue

Hello, i was trying to change the default value of thumbnail Image display in Image Gallery with Slideshow plugin but i can’t able to figure out where it needs to set. Can anyone help on this ?

Default value on the settings-> 170by170px.

http://ww.wp.xz.cn/extend/plugins/image-gallery-with-slideshow/