VLM is "Vivid Light Magenta" not "Very Light Magenta". The Epson's only have 2 Magentas VM and VLM. So you are correct the VLM is the same as light magenta. If you're ever in doubt, try to stick the cart in. I haven't used a 3880 but in every other Epson I've used each cart only fits in the proper spot.