Here are some quotes from the download from Equitablemath.org, as examples of when "we see white supremacy culture in the mathematics classroom:"
The focus is on getting the “right” answer
Students are required to show their work
Too often students are tracked based on the notion that adults know what the right thing is for them
Math is taught in a linear fashion and skills are taught sequentially
teachers or other experts can and should correct mistakes
Some of the other ideas they raise have validity, but having nothing to do with racism, and relating to generally effective student interaction, teaching methods, and encouraging student participation & engagement.