question about banner ads

[luphie]

hello, i have bought banned ads (header ads) for a forum for december and january next year. but i still don't understand the number 3 on this day. after i bought it, it turns out that i can still buy banner ads in the same month. so does it mean that even though i have booked in that month someone can still buy it too? (previously i thought that banner ads are like sticky threads that 1 post/ads belongs to 1 person only)
*I just read on infocenter, that there are 4 rotations on ads. what does that mean? thank you.

 

[EpicNPC]

Each location can have 4 banners in rotation, so each purchase received 25% of the impressions.

 

[luphie]

Each location can have 4 banners in rotation, so each purchase received 25% of the impressions.

how is the rotation determined? will there be a notification when my banner schedule is displayed? or is it every 6 hours with the same hours continuously, for example I am at 12 pm - 6 am or what?

 

[EpicNPC]

it's random.

 

[luphie]

it's random.

ok, thank you