Marks Conversions with high IP-Similarity.
To reproduce this reason check the IP Address column inside the conversion report for conversions with the same IP range (same 1st 3 blocks), i.e.:
Having over 10%-15% of conversions from the same IP range is highly suspicious as these similar IPs indicate users coming from the same street, building or cellphone tower.
A very common tactic among fraudsters is making a conversion and then resetting their IP to get a new but similar one, in order to artificially increase the amount of conversions while avoiding duplicate IPs.