To further clarify:

Say you control one Hinata and three Battlefield Thaumaturges, and cast Crackle with Power with five targets, two of which are creatures, and an X of 5. Then Crackle with Power will normally cost {5}{5}{5}{R}{R} = {15}{R}{R}. But—

• the spell's cost is reduced by {5} times the number of Hinatas you control, so by {5}, and

• the spell's cost is reduced by an additional {2} times the number of Battlefield Thaumaturges you control, so by {2} + {2} + {2} = {6},

for a total cost reduction of {11}, so that the cost of Crackle with Power is {15}{R}{R} = {11} = {4}{R}{R}.

Now take the same scenario as before, except you control only one Battlefield Thaumaturge. Then the cost reduction is {5} + {2} = {7}, so that the cost of Crackle with Power is {15}{R}{R} = {7} = {8}{R}{R}.