Partnership Distributions Accounting

In the accounting treatment of partnership distributions, there is a theoretical question: if an entity contributes $1,000 and expects to receive $300 per year over a five-year period (total return of $1,500), should the first $1,000 be considered a return of capital, with subsequent distributions (i.e., years 4 and 5) treated as capital gains? Or should the annual distributions be split between return of capital and capital gains (for simplicity, if using the straight-line method, then each year's distribution would consist of $200 as return of capital and $100 as capital gains)? I am new to this forum, and I appreciate your time and consideration.