Yes, that test looks to be really accurate, with a sensitivity of 99.63% and a specificity of 99.93% (https://www.rapidtest.com/pdf/Syphilis_Serum_WB_Plasma_RapiCard%20176501-40-12%20(2017-2-9).pdf)
This means that it can accurately identify those who are positive and those who are negative at almost 100%. (No test is 100%.) Since you did it after 90 days, it's conclusive. I'm not sure what your sore was - how long did it last? A chancre lasts about 3 weeks, usually, and is painless.
If you're still concerned, you can get a blood test done by your doctor to confirm.
What was your exposure?