CCS/TMS320C6748: How to understand FFT results

Tool/software: Code Composer Studio

I use C6748 board and CCS 8.1.0 version.

I tried to use the DSPF_sp_fftSPxSP function on dsplib to do a Real FFT.

So I made an input array as shown in the picture below.

I plotted the real and imaginary parts to analyze the FFT results

First is a real number graph.

The second is the imaginary part graph

The question is, why do the graphs that have the same amplitude have different values ​​in the real part?

I know that the library in dsplib alternates between real and imaginary sequences.

So I put 0 in the imaginary part of the input.

Likewise, in the graph, even-numbered parts in real array and odd-numbered part are drawn in imaginary array.

Let me know if I miss something