integration error

[ayari_mustapha]

hello all. I want to implement an algorithm to calculate velocity from acceleration samples. I have found in this document attached description on how to reduce errors of the integration,

https://www.nxp.com/docs/en/application-note/AN3397.pdf 

I want to use this formula, but I am confused on what each term means, and also the homogeneity of the equation, since (Samples * T) is an Area and Sample_n is not. could anyone help me. if I'm posting this question in the non right place could anyone guide me where should I post it