I see two capacitors for VDDA and two capacitors for VREFH pins on TWR-K60N512. They are both X7R chip capacitors, 100nF and 10nF.
What is the reason to use two of them? Is it sufficient to use a single 100nF X7R capacitor near VDDA and VREFH pins of microcontroller?
They are bypass capacitors. They have different capacitance, ESR and ESL that help to eliminate the noise at different frequencies.
If you put only one, the noise at a frequency range may effects to working of the chip.
You can get more information if google with "bypass capacitor combination"
Regards