Daniel 12:12 (1335/ 1305)

Hi, I was doing some research on Daniel and I was wondering if you can expound on Daniel 12 and the 1305. I'm researching the constuction of the number in Hebrew and trying to understand if the number should be 1305 and then the 30 years is separate or if possible this could be a copyist error (which we cannot prove at this time) but my personal research makes me believe the numbers should be 1290 and 1305 not 1335. What are your thoughts? Tory