How to calculate the "Count" next to Molten Strike of the Zenith in POB

Can someone please explain to me why this guy build he put 18 in "Count" tab of Molten strike of the zenith in the Skill tab
Like how to calculate it?
Thank you!
https://pobb.in/2Ghd6Zg7daOd

My understanding is:

18 is the number of hits each fifth hit does (the 76% less damage in the custom settings is to account for the other 4 hits), 18 would be calculated from (5 [base projecticles] + 4 [GMP support])*2[returning projectiles]. This is why you see 20 in there for high-end PoBs, since they use awakened GMP which gives an additional projectile (and thus 2 returning ones).

To get the full double hit on a single target I‘m pretty sure you need some amount of „reduced projectile damage“.

Thank you! That makes sense to me, but in this POB he change the count to 24 and make me confuse again, he uses AGMP, shouldn't that be (5+5)*2=20 like you said?
https://pobb.in/q5eu74foVe1h

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SadmannWalking wrote:

Thank you! That makes sense to me, but in this POB he change the count to 24 and make me confuse again, he uses AGMP, shouldn't that be (5+5)*2=20 like you said?
https://pobb.in/q5eu74foVe1h

Might be Snipers mark, technically that should add either 4 or 2 hits (not sure at what point it fully shotguns), no clue why it is not calculated in in the first PoB.

Thank you for explaining, really made me understand better!