When an echo reply packet is received, the data is compared with the sent data. When a wrong byte is detected the command displays a report with the differences.
The first row (the first 8-bytes of data after the ICMP header) should include the time stamp (if data is at least 8-bytes), this value is not taken into consideration for the comparison. The remaining rows represent the data (padded pattern) received/sent, with each byte being compared for differences.
Print the space before (not after), to add an extra space after cp:/dp: for better readability when the first time stamp octet is not zero-padded, and to remove trailing spaces in the output.
Before:

cp:99  0  0  c  1  5  c  0␣
    ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd␣
    ...

After:

cp: 99  0  0  c  1  5  c  0
     ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd
     ...