The test line got lighter!

Hi,

I tested a very positive pregnancy test at the day of my expected period , but after 2 days I tried another one and the line was much lighter!!

What was different between the two tests, that i took the second one and the urine sample was so diluted but the first one was after I waited 2 hrs before using the toilet.

Does the timing and the concentration of the urine sample affect the results??

Thank you.