The title, "The Computation" already gives us a clue, because there's no way a Renaissance poet is going to write an entire poem about adding up numbers. This work is addressed to the speaker's lover, in an attempt to show her how much the speaker cares about her. He is so slavishly devoted that he cannot "divide" his thoughts from her for a thousand years. Although there is no suggestion of a breakup, he is unsure about whether she will continue to "favor" him. Also, it is notable that the poem seems somewhat egotistical, with the speaker talking about his own emotions and experiences, and not giving us any idea of what his lover is like.
"The Computation" is an example of a generic love poem that is more focused on the use of wit and figurative language than on the character of the beloved.
"The Computation" likely concerns a couple in the first, passionate stages of love, like Romeo and Juliet after they have spent a night together.