I wonder how you arrived at 37,800 anyway - should be perhaps 15,000(?)
Being a retired "bean counter", I play with many numbers. I keep track daily of my "Experience points" and I've been doing it for years (yes, I must be a lunatic to do this...but I do). The 37,842 is the difference between my 6/3 total of 16,219,036 and my 6/4 total of 16,256,878.
I don't buy extras from WGT, but others might.
And I will buy the 40% Boost when I hit 4,000!