The output of jstat with -gccause option can contain old space utilization in percent which is greater than 100.

The example output looks like this (see the value 131.57 in O column):
S0 S1 E O P YGC YGCT FGC FGCT GCT LGCC GCC
0.00 100.00 43.17 131.57 70.03 21 47.335 2 1.161 48.496 Allocation Failure No GC