This is wrong because they should be mutually exclusive, and that's literally a written rule that's been documented. This Thursday is restricted for the Thursday within the seven day period you're in, regardless of where that starts, and next Thursday is the Thursday within the next 7 day period. It's not hard to understand the rule, but I still qualify it every time I use the phrase 'next thursday'. Usually by saying something like 'lets hang out next Thursday, not this one but the next one after that'.