Upgrading from Master 100 tons

I have recently got my Masters 100 ton licence and I want to upgrade to either 200 tons or 500 tons, but I’m finding all the information for what I need a little confusing. I currently work on a super yacht of 846 GRT as first mate. I have currently 902 service days which half of these are actual sea days (4 hours or more underway). Can I upgrade to my 500 tons or do I need to upgrade for my 200 ton first? Also what else do I need to take to complete the upgrade? When it says total service days does that mean days on the boat or is that only counted if underway for more than 4 hours?