That is the law of large numbers doing its work.
Another thing...
A global: If loot greater than or equal to 50 (on most mobs), then announce global, play trumpets, play swirly.
A hof: If loot is greater than or equal to 50 (on most mobs), AND greater than the lowest recorded global, then announce HOF, play louder trumpets, play bigger swirly.
I can get a hof out of 10 PED from a fugabarba if it happens right after some globals expire from the list. Some one right before me could have killed a feffox for 40 ped and it wouldnt even be a global.
I've had runs hours long in which I didn't get ANY swirlies, and profited well.
I've had runs in similar time spans where I did get globals and lost ped.
And vise versa.
Those swirls are just entirely visual
They are not something extra being injected from your prior hunts.
What you are 'seeing' you are making up as you go.