It's a kind of labour seal issued from Ministry of labour in Myanmar. It's said that you get your employment contract stamped at a labour office but those are normally for labourers, not at professional level. Don't know why they demanded it. But the embassy didn't ask if you are director level and above. That's the situation back in Oct. I don't have the latest info.
It opens at 6:30 am MM time sharp. And you'll only have a few mins before the slots run out. You have to be very very quick. For me, I wrote down all the items i need to fill in such as name, email, pp number, ph number on a notepad and by 6:30 am, I clicked the link, went in, copied and entered all my info, chose the visa type (Any type of visa will do. Don't sweat much), all within like 30 secs. I managed to get it. Good luck.