简单数学问题求助

[faker1]

/***
 有一段 go 代码如下， 这个 ```result ```值 在某个区间是一样的？
***/
package main

import (
	"time"
	"log"
)


func PrevSlot(now int64) int64 {
	// now = time.Now().Unix()
	var blockInterval = int64(10)

	result := int64((now-1)/blockInterval) * blockInterval //  这个值在咋一样呢？弄了半天不懂
	log.Println("PrevSlot:", int64(result), int64((now-1)/blockInterval), now)
	return result
}


func main() {
	//fmt.Println(15 /2)
	ticker := time.NewTicker(1 * time.Second)
	for {
		<-ticker.C

		now := time.Now().Unix()
		PrevSlot(now)
	}

}

/**
output:
2019-01-16 10:58:31.668597 I | dpos.go: PrevSlot: 1547607510 154760751 1547607511
2019-01-16 10:58:32.668649 I | dpos.go: PrevSlot: 1547607510 154760751 1547607512
2019-01-16 10:58:33.668568 I | dpos.go: PrevSlot: 1547607510 154760751 1547607513
2019-01-16 10:58:34.668572 I | dpos.go: PrevSlot: 1547607510 154760751 1547607514
2019-01-16 10:58:35.668547 I | dpos.go: PrevSlot: 1547607510 154760751 1547607515

 */