That's just the size of the files (if you remove the signatures and unpack UPX) are different and are 5,376,512 bytes for 3.5.5.45974 and 5,385,256 bytes for 3.5.5.45918.
As there's no stable thread...
3.5.5_45395 magnet: magnet:?xt=urn:btih:CDEEB509D694DC43B2A93443D4EF15EAB9A8F07F
File size: 3,19 MB (3 350 648 bytes) / MD5: 0F07BA2B4D0FA0CCBC028C44157E04D5
Digitally Signed: BitTorrent Inc. 29 Oct 2019 23:22:02
No changelog at time of posting.