Startup offered less cash but a real chunk of equity and I genuinely don't know how to evaluate that

Series A, maybe 18 months of runway based on what they told me, offer is about 15% below my current base plus 0.3% equity over four years. I've never had to think about a strike price or a 409A valuation before and every calculator I find online assumes I already understand the inputs. Not asking anyone to do my math for me, just: what actually matters here beyond 'equity is usually worth zero'? Is there a question I should be asking them that I haven't thought of?