Question of Using API: Variable Postfix

Hi Everyone,
I hope you're all doing well.
I'm new to here and I want to use the API on Census to get the data from ACS.
Here's the link to the variables.
What I get confused is that the explanation of variable "DP02_0059E, DP02_0059M, DP02_0059PE" are identical and I don't understand the postfix of each variable. I cannot find the 'subject definition' document either. (

Does anyone know what does the postfix refer to?
Any help you may provide will be highly appreciated.

Thanks a lot in advance.

Best regards,