Holdem Spread Limit Bets

[dakine]

Again, I and my friends are novice players. In a spread limit betting structure, $1-4 pre-flop & 3 card flop, $4-8 turn & river flop. I am raising the $1-4, to $4, two more raises are allowed after my raise. Can the next raise go over the $4, (raise to $8), or is the raise capped at $4? Now, I searched most of the forum looking for this topic/answer, but I'm 69 years old and am falling asleep, so I can't complete the search. Simple answes would suffice, no critiques, please! Edit. The raise is to $4.