Looking great! I know exactly what you're talking about with the API test kit. It helps to do exactly what you are doing, look from different angles. What I do is hold the tube against the card at a 45 degree angle from horizontal a foot or so under a light like the kitchen table, then stand it up on the card on the counter, and you can usually gauge the reading that way. If there is any hint of red, you're more towards 40 than 20. 20 is pretty much orange however you look at it.