I was originally open water certified by SSI, but am now taking some PADI courses. I still use my dive tables from SSI, which are based on the Navy tables. When working my dive profile, I sometimes run into situations where my Repetitive Group is different than my PADI teammates. The instructor will check my work on my tables, and find them correct, however the Repetitive Group IS different from the PADI answer. She mentioned that the reason may be because the SSI tables are based on the Navy tables, and therefore not as conservative as the PADI tables...or that perhaps my tables are defective and should be replaced. She mentioned that she thought there was a website that gave information about serial numbers of dive tables that were defective, but she didn't know the website address. Does anyone know the web address of such a website, or offer any explanation as to the differences I'm experiencing in SSI versus PADI dive tables? Any suggestions? Thanks.