There's not enough information in that comment. What kind of Math courses did he take? Did he ever take an intro to proofs course? Did any of his Math courses e

There's not enough information in that comment. What kind of Math courses did he take? Did he ever take an intro to proofs course? Did any of his Math courses emphasize proofs? All the proof heavy courses I've taken, whenever new notation was introduced the professor would explain how to interpret it. And if they didn't someone would raise their hand and ask what it meant. Which brings me to another point, was OP an active learner? Did he ask questions when he didn't understand?