I don't think there is a really a problem here. You are basically comparing apples to orange to bananas and wondering why they aren't the same... and you are not the first to wonder why because it confuses the heck out of everyone. You are looking at 3 different things: Rainmeter (via the gadget) which is getting information from Windows performance counters database, Task Manager which is getting information from some source that Microsoft hasn't clearly documented, and (I think) SysInternals ProcMon (??) which has its own way of gathering this information also not really documented but probably by querying that process' data directly.
All three of those things (performance counters, task manager, procmon) are from Microsoft, so it might be best to ask them why their own stuff is inconsistent. For the purpose of Rainmeter, all that skin authors can do is report whatever the performance counters database is telling us.