I think you must have changed the default for "SNP window size threshold." and "Minimum segment cM size" to get such a large total for such a small largest segment size.
To test this, I changed the defaults for these and compared myself to my lowest match and got the following:
Largest segment = 9.0 cM
Total Half-Match segments (HIR) = 561.4 cM (15.659 Pct)
133 shared segments found for this comparison.
145586 SNPs used for this comparison.
52.264 Pct SNPs are full identical
This shows how important it is not to change the default settings.