You can always submit your measurement after placing the order. For now, just select Customize with Made to Measure, click Add to Shopping Bag and complete order. Later on go to Account section, visit My Orders page and submit your latest measurement.
If your bare chest size measurement is 40 inches, you should select size 40 only from the product page. The "Top Chest" attribute in the size chart refers to the garment's chest size. It is inclusive of the required 3 to 4 inches loosening, to ensure the right fit.
If your bare chest measurement falls between 2 sizes i.e 37 inches, you should select size 38.
https://www.utsavfashion.com/product/embroidered-dupion-silk-kurta-set-in-light-green-mpw3370641Embroidered Dupion Silk Kurta Set in Light Greenhttps://medias.utsavfashion.com/media/catalog/product/cache/1/small_image/295x/040ec09b1e35df139433887a97daa66f/m/p/mpw3.jpg51.264USDInStock/men/men/plus/men/festive/men/art silk/men/dupion silk/men/green/men/kurta pyjama/men/resham/men/traditionalEmbroidered Dupion Silk Kurta Set in Light Green <ul><li> Enhanced with Resham and Stone Work in Ornamental Motifs</li><li> Available with Art Dupion Silk Churidar in Light Beige</li><li> Beige Art Silk Dupatta is also available</li><li> Do Note: Dupatta and mojari shown in the image is for photography purpose. Half to one inch may differ in measurement. (Slight color variation is possible.)</li><li> Half to one inch may vary in measurement</li></ul>USDtype_new:Kurta Pyjamacolorfam:Greenfabric:Art Silk, Dupion SilkGreenArt Silk, Dupion SilkKurta Pyjama11%-20%MenWithin 15 days, More than 15 DaysReadymadeFestiveMenswearResham, Traditional34, 36, 38, 40, 4244, 46, 48, 50, 52, 54, 56, 58, 60