Yes, we need to know that. Since the source water seems to be around 8, and the high range test gives that number, you should be using the high range for all tests from now on.
When the pH is above the range of a test kit, such as being higher than the highest range on the basic test kit in this case, any pH above that number will be that number. Example, if you are using a test kit with a range of 6.6 to 7.6 and the pH of the water being tested is 8, 8.6, or 9, the test will show it as 7.6 because that is as high as the range goes. But using a high range test kit with say a range of 7.5 to 9 will show the correct pH within that range. This works in reverse too, for low pH.
So if you used the high range test on the source water and it is 8, and you used this same test for the tank, the result should tell you the tank pH accurately.