Confirm, boxes indicate only the transcibed part of the gene: black boxes are thus exons, with thicker parts representing CDS and thinner parts represent the UTR regions, not the promoter. If gene is to be read from left to right, the 3rd exon is different in the 2 isoforms
If the gene is on the minus strand then the thinner bar to the right is the 5'-UTR, the thicker bar is the protein-coding exon, which should start with ATG, and very thin lines are introns.