Schema maps as closely to ACSS as Figma allows - but Figma is a design tool, not a browser. A few things don't fully translate.
ACSS uses clamp() to fluidly scale values between viewports. Figma variables can't do this - they resolve to one value per mode. So the framework uses two discrete modes (Desktop and Mobile) to approximate what the browser does fluidly. See Responsiveness.
ACSS generates scales from a base size and a ratio. Figma variables don't support formulas, so scale values are pre-calculated and entered manually. When you change the base or ratio, you need to recalculate each step yourself. See Working with Scales.
Properties like line height are typically set as percentages in CSS. Figma variables don't support percentage values, so these are set manually on each text style rather than through the variable system. See Text Styles.
There's no way to automatically export Figma variables into ACSS. The handoff process is manual - you transfer your variable values from Figma into the ACSS dashboard yourself. The naming maps directly, so it's straightforward, but it's a manual step.
ACSS 4 uses OKLCH color space in the plugin, but Figma currently supports HSL. We're waiting for Figma to enable OKLCH color profile support, or research for an acceptable solution.
These limitations affect automation and in the case if color accuracy. The variable architecture, naming, and semantic structure all carry over faithfully - certain values just require manual steps that ACSS handles automatically in code.