fix full respawn calculation

(cherry picked from commit 7babbac)

src/main/java/server/maps/MapleMap.java

@@ -3530,12 +3530,12 @@ private int getNumShouldSpawn(int numPlayers) {
         System.out.println("----------------------------------");
         */
 
+        float maxMob = monsterSpawn.size() * getWorldServer().getMobrate();
+
         if (YamlConfig.config.server.USE_ENABLE_FULL_RESPAWN) {
-            return (int) Math.ceil((monsterSpawn.size() - spawnedMonstersOnMap.get()) * getWorldServer().getMobrate());
+            return (int) Math.ceil(maxMob) - spawnedMonstersOnMap.get();
         }
-
-        int maxNumShouldSpawn = (int) Math.ceil(getCurrentSpawnRate(numPlayers) * monsterSpawn.size() * getWorldServer().getMobrate());
-        return maxNumShouldSpawn - spawnedMonstersOnMap.get();
+        return (int) Math.ceil(getCurrentSpawnRate(numPlayers) * maxMob) - spawnedMonstersOnMap.get();
     }
 
     public void respawn() {

src/test/java/server/maps/MapleMapTest.java

@@ -0,0 +1,31 @@
+package server.maps;
+
+import org.junit.jupiter.api.Test;
+
+class MapleMapTest {
+
+    @Test
+    void randShouldIncludeEntireRange() {
+        Map<Integer, Integer> rands = new HashMap<>();
+
+        final int rounds = 100_000;
+        for (int i = 0; i < rounds; i++) {
+            int randomValue = Randomizer.rand(-5, 5);
+            rands.compute(randomValue, (k, v) -> v == null ? 0 : v + 1);
+        }
+
+        assertFalse(rands.containsKey(-6));
+        assertTrue(rands.containsKey(-5));
+        assertTrue(rands.containsKey(-4));
+        assertTrue(rands.containsKey(-3));
+        assertTrue(rands.containsKey(-2));
+        assertTrue(rands.containsKey(-1));
+        assertTrue(rands.containsKey(0));
+        assertTrue(rands.containsKey(1));
+        assertTrue(rands.containsKey(2));
+        assertTrue(rands.containsKey(3));
+        assertTrue(rands.containsKey(4));
+        assertTrue(rands.containsKey(5));
+        assertFalse(rands.containsKey(6));
+    }
+}