I have the same situation here. I just purchased a brand new SanDisk Ultra II 240GB and installed SanDisk SSD Dashboard. The S.M.A.R.T. report marks an exclamation point at ID 232, Available Reserve Space and indicates my drive health condition is Poor.
Certainly this surprises me since the SSD is just 2 weeks old and I only have installed Windows and some other software. This problem encourages me to try using a few third-party HDD check tools such as CrystalDiskInfo, HDD Scan, HD Tune. All of them report my SSD is OK, every S.M.A.R.T. attribute is green. Then I used CrystalDiskMark to benchmark the performance. The result is satisfactory as read/write speed is as advertised.
When I come to this forum, I notice many buyers are having the same issue: this and this. So I think this is more likely of Dashboard problem than the SSD itself.
SanDisk, you make me concerned about your product quality. SanDisk SSD Dashboard is a first-party software, nevertheless, it confuses customers, makes inaccurate calculation. Currently the latest version is 1.4.1, release date July 20, 2015 as shown here but you have not fixed it for quite a long time. Unless my SSD is from a batch of manufactured defective drives, you should resolve it ASAP.