gc logs [Full GC (System)

[bhm]

please help me understand in following 2 line if
Full GC (System)
means this is caused due to System.gc() call ?

16.620: [Full GC 16.620: [CMS: 8849K->11102K(245760K), 0.9170804 secs]
34309K->11102K(277440K), [CMS Perm : 27162K->26963K(27208K)],
0.9180653 secs] [Times: user=0.91 sys=0.00, real=0.92 secs]
22.286: [Full GC (System) 22.286: [CMS: 12805K->14033K(245760K),
1.1113881 secs] 24546K->14033K(277440K), [CMS Perm :
36005K->35855K(44944K)], 1.1217119 secs] [Times: user=1.12 sys=0.01,
real=1.12 secs]

I couldnt find any explaination in following 2 links
http://www.sun.com/bigadmin/content/submitted/cms_gc_logs.jsp
http://www.oracle.com/technetwork/java/example-141412.html

Thanks.