In the EVK user guide:
MAX40213 Evaluation Kit - Evaluates: MAX40213
1. I've no idea how the generated input current step is calculated, could you please explain it?

And I've tried to measure the output OUTP and OUTN of circuit 1 below:

Test environment: VCC=3.3V, GAIN=150k, input floating(there is 49.9ohm R4 connecting I_IN to GND so actually it's not floating)
Blue line- OUTN, yellow-3.3V(AC coupled).

2. I don't understand why there is about 396MHz sinusoidal waveform at the output.