The test solution actually has quite a broad range for the test strips. If you look at your pot of test strips it will have a range or perhaps 2 or 3 ranges for test solutions.
My Caresens test strips have a low range which is 2.9 - 3.7, so the low control solution should read within that range and the high range is 11.1-15.1 so the high control solution should fall within that very broad range, which just reinforces the fact that they are not that accurate, when the known solution has to read between those values.
They used to recommend in the instruction manual that you tested a strip from each new pot that you opened and I used to do that, but haven't done it for years now.