diff --git a/server/src/main/kotlin/suwayomi/tachidesk/manga/impl/Chapter.kt b/server/src/main/kotlin/suwayomi/tachidesk/manga/impl/Chapter.kt
index d67138f1..727a6596 100644
--- a/server/src/main/kotlin/suwayomi/tachidesk/manga/impl/Chapter.kt
+++ b/server/src/main/kotlin/suwayomi/tachidesk/manga/impl/Chapter.kt
@@ -298,18 +298,28 @@ object Chapter {
         prevNumberOfChapters: Int,
         updatedChapterList: List<ResultRow>,
     ) {
+        val log =
+            KotlinLogging.logger(
+                "${logger.name}::downloadNewChapters(" +
+                    "mangaId= $mangaId, " +
+                    "prevNumberOfChapters= $prevNumberOfChapters, " +
+                    "updatedChapterList= ${updatedChapterList.size}, " +
+                    "downloadAheadLimit= ${serverConfig.autoDownloadAheadLimit.value}" +
+                    ")",
+            )
+
         // convert numbers to be index based
-        val currentNumberOfChapters = (prevNumberOfChapters - 1).coerceAtLeast(0)
-        val updatedNumberOfChapters = (updatedChapterList.size - 1).coerceAtLeast(0)
-        val numberOfNewChapters = updatedNumberOfChapters - currentNumberOfChapters
+        val newNumberOfChapters = updatedChapterList.size
+        val numberOfNewChapters = newNumberOfChapters - prevNumberOfChapters
 
         val areNewChaptersAvailable = numberOfNewChapters > 0
-        val wasInitialFetch = currentNumberOfChapters == -1 // has to be -1 - due to converting to index based 1 chapter will be 0
+        val wasInitialFetch = prevNumberOfChapters == 0
 
         // make sure to ignore initial fetch
         val isDownloadPossible =
             serverConfig.autoDownloadNewChapters.value && areNewChaptersAvailable && !wasInitialFetch
         if (!isDownloadPossible) {
+            log.debug { "download is not allowed/possible" }
             return
         }
 
@@ -317,19 +327,20 @@ object Chapter {
 
         // make sure to only consider the latest chapters. e.g. old unread chapters should be ignored
         val latestReadChapterIndex =
-            updatedChapterList.indexOfFirst { it[ChapterTable.isRead] }.takeIf { it > -1 } ?: (updatedChapterList.size - 1)
+            updatedChapterList.indexOfFirst { it[ChapterTable.isRead] }.takeIf { it > -1 } ?: (updatedChapterList.size)
         val unreadChapters =
             updatedChapterList.subList(numberOfNewChapters, latestReadChapterIndex)
                 .filter { !it[ChapterTable.isRead] }
 
         val skipDueToUnreadChapters = serverConfig.excludeEntryWithUnreadChapters.value && unreadChapters.isNotEmpty()
         if (skipDueToUnreadChapters) {
+            log.debug { "ignore due to unread chapters" }
             return
         }
 
         val firstChapterToDownloadIndex =
             if (serverConfig.autoDownloadAheadLimit.value > 0) {
-                (numberOfNewChapters - serverConfig.autoDownloadAheadLimit.value).coerceAtLeast(0)
+                (numberOfNewChapters - serverConfig.autoDownloadAheadLimit.value - 1).coerceAtLeast(0)
             } else {
                 0
             }
@@ -340,10 +351,11 @@ object Chapter {
                 .map { it[ChapterTable.id].value }
 
         if (chapterIdsToDownload.isEmpty()) {
+            log.debug { "no chapters available for download" }
             return
         }
 
-        logger.info { "downloadNewChapters($mangaId): Downloading \"${chapterIdsToDownload.size}\" new chapter(s)..." }
+        log.info { "download ${chapterIdsToDownload.size} new chapter(s)..." }
 
         DownloadManager.enqueue(EnqueueInput(chapterIdsToDownload))
     }