My 0.02€ - can it include a way of proportioning "work to date" - ie let's say the startup has been incubating for 2 years, and it's now found 2 co-founders...

My 0.02€ - can it include a way of proportioning "work to date" - ie let's say the startup has been incubating for 2 years, and it's now found 2 co-founders... How do I model that ?