Definition
A concentration limit is the level above which a substance must be reported or is restricted. The most common limit in articles is 0.1 percent by weight, which triggers REACH Article 33 and SCIP.
REACH (SVHC in articles)
RoHS
0.1 percent per homogeneous material for most restricted substances, and 0.01 percent for cadmium.
The catch is the reference base. RoHS measures against a single homogeneous material, while REACH measures against the whole article, so the same percentage can mean very different real quantities. Always check which base a given rule uses before comparing numbers.
Note: general educational information, not legal advice. Check the official source before relying on it.