Red Hot Jackpots Slot Machine

Hi everyone.
I was wondering if anyone familiar with Red Hot Jackpot machines might be able to help with a question about its progressive jackpots. My local casino has about 20 of these machines scattered throughout the casino (1 cent denomination, max bet to enable Red Hot Jackpots is 100 credits), and I really enjoy playing them, but I've noticed something quirky about the progressive jackpots.
If, for example, I hit the initial bonus round and win only the 'Jackpot!' progressive (the smallest of the 4 progressives), I've noticed that the amount I'm awarded at the end of the jackpot matches neither the amount on the progressive meter when I first hit the jackpot nor the amount on the meter at the end of the bonus round...it's often a couple dollars more or a couple dollars less. Let's say that the meter is at $6.00 when I initially hit the bonus round, and $7.00 at the conclusion of the bonus round. Sometimes, I might be awarded something like $5.50 (the minimum for this jackpot is $5), while other times I'm awarded around $10. That said, I'm trying to figure out at what point a progressive jackpot is actually awarded to a specific machine.
A while back, I entered the bonus round, collected 20+ Red Hot Jackpot symbols in the bonus, and was consequently awarded the third tier 'Hotter Jackpot!'. When I initially entered the bonus round, I recall noticing that the third tier jackpot was a little over $170, and right when I hit the 20th Red Hot Jackpot symbol and won the 'Hotter Jackpot!' progressive I noted that it was up to $178. I thought I was going to win that $178 (in addition to the other winnings from the bonus round), but at the end of the bonus I ended up being awarded a total of only around $146. Not bad, but I was kind of bummed that I wasn't awarded the $178 progressive.
Could it be that with 20 machines throughout the casino connected to this progressive, the progressive meters just aren't updating and resetting fast enough? My guess is that since my bonus round wasn't yet complete when I hit the $178 'Hotter Jackpot!' (I still had more free spins), someone else hit the same jackpot AND concluded their bonus round between the time I hit the jackpot and concluded my bonus round. If that's the case, then maybe the progressive value is actually locked in only upon the conclusion of the bonus round, and perhaps the progressive meters aren't updating instantly. The machines are fun to play, but I just wish I could figure out this mystery regarding the progressives!
Thanks to anyone who might be able to help!