Another /particle question

A very quick question, what does it want from me? execute at @e[tag=event_center,limit=1] as @a[distance=..15] at @s run particle minecraft:dust{color:[0.24,0.66,0.89],scale:1} 0.5 0.8 1.0 0.6 ~ ~1 ~ 0.1 0.1 0.1 0 1