If my maths are correct, this works out to about 0.4mm. If you only ever do woodworking on it, there really is very little point in fixing this. Different story for metalworking, though. If you simply want a flat reference platform, you might want to consider putting a frame around the table and flooding it with a fine epoxy resin (after making sure your table is perfectly level). This can easily be machined and replaced, and won't cost an arm and a leg. OTOH, it's obviously not as durable as a metal surface.