This is normal and has to do with the way the filer calculates the util% metric (it's not the average over all disks but only the disk with the highest utilization, for example). This is only a display problem and it is even documented (either in the man-page for the sysstat command, or in the admin guides, don't remember where)
You can ignore these bogus lines. However, having a disk utilization of 100% for longer periods is in itself a problem that you should look into. You might have a hotspot disk or some other problem
Michael is correct sysstat only measures the highest number achieved on a single disk in the controller. This is not the average of all disks. Again as MIchael stated having 100% for long period of times is not a good thing. There is a better way to do disk monitoring for utilization of disks using advanced privilege sessions.