Patrick Mathieson‘s answer is spot-on.
I’d dive in one level deeper and say most VCs that manage less than say $300m in a fund will do a smaller investment so long as they (1) can buy at least 7.5%-10% of the company and (2) have not just pro-rata rights but also an implicit opportunity to invest more in the next round.
I’ve done several of these and they’ve mostly worked out well. If you can’t invest more later, though, it doesn’t really structurally work, because it’s an immaterial % of the fund itself.
If I’d invest later, but can invest now and believe in the opportunity and team — why not?