Please update your PSOC Creator to PSoC Creator 4.1 (18.104.22.16886).
Welcome in the forum.
For every bit (byte) the SPI interface gets, one bit (byte) is returned immediately. When the very first byte is sent, the interface does not "know" yet what to answer, so a dummy byte is returned which should be skipped.
SPI has no read command, so you must send dummy bytes to retrieve the information wanted.
There are APIs and #defined constants to check (and wait for) bytes received. Reading from SPI when nothing was received results in unknown data.
On UART side: your variables bx, by and er are 16 bit integers, only the lower 8 bits will be transmitted through the UART.