diff --git a/src/record_iterator.rs b/src/record_iterator.rs
index cd9e165..54a3a31 100644
--- a/src/record_iterator.rs
+++ b/src/record_iterator.rs
@@ -16,9 +16,9 @@ impl<'a> RecordIterator<'a> {
         let total_records = r701.get_total_record_count()?;
 
         // Calculate the sequence number on which the last record resides and
-        // the position of the first useless byte
-        let sequence_number = total_records * 12 / 1024;
-        let first_useless_byte_index = (total_records * 12 % 1024) as usize;
+        // the index of the first `ff` byte, avoiding overflows
+        let sequence_number = (total_records as u32 * 12 / 1024) as u16;
+        let first_useless_byte_index = total_records as usize * 12 % 1024;
 
         // The endpoint expects the first block of records to be sent first
         r701.get_record_bytes(total_records, 0)?;