Hi, @ghubs. I found this post on learning rates very helpful: Determining when you are overfitting, underfitting, or just right?.
Regarding the notation for the learning rate: are you familiar with scientific notation? If not, Khan Academy is a fantastic free resource, with a good series on the topic: https://www.khanacademy.org/math/pre-algebra/pre-algebra-exponents-radicals#pre-algebra-scientific-notation
If you’re already familiar with scientific notation, you might be used to seeing it notated as something times 10 to a power, and this notation using e is actually equivalent. The ‘e’ represents “10 to the power of,” not the number e! https://en.wikipedia.org/wiki/Scientific_notation#E-notation
So 1e-3 == 1 * 10^(-3) == 0.001. If the number in the decimal place needs to be something other than 1, you’ll use that number. For instance, if you needed to express 0.05 in this notation, you’d have 5e-2, i.e. “5 times 10 to the power of -2”.
I hope this helps!