Hours are a bit confusing, but the easiest way to think about it is that by spending $X you're raising your cap by X00 for 30 days. When you use hours, they regenerate after 30 days. So if you spend $4 (gain 400 hours) on September 1st, bot 200 hours September 3rd (for example), spent $5 (gain 500 hours) on September 5th, The $4 drops off October 1st (so your cap goes down 400 hours), you will regain 200 hours Oct 3rd, and the $5 drops off October 5th (your cap goes down 500 hours again). So it sounds like whatever you bought a month ago today just dropped off, and you can either wait for hours to regenerate or top up more & you will also regenerate more hours over time. Hopefully that makes sense at all. I know it's confusing.
