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/woven-art-silk-kurta-jacket-set-in-beige-and-pink-mgv13351843870Woven Art Silk Kurta Jacket Set in Beige and Pinkhttps://medias.utsavfashion.com/media/catalog/product/cache/1/small_image/295x/040ec09b1e35df139433887a97daa66f/w/o/woven-art-silk-kurta-jacket-set-in-beige-and-pink-v1-mgv1335.jpg107.2134USDInStock/men/men/plus/men/reception/men/wedding/men/festive/men/art silk/men/beige/men/pink/men/kurta pyjama/men/buttons/men/traditionalWoven Art Silk Kurta Jacket Set in Beige and Pink <ul><li> Art Silk Kurta in Beige</li><li> This Readymade attire is Enhanced with Buttons and is Crafted in Chinese Collar Neck and Full Sleeve</li><li> Available with an Art Silk Aligarhi Pant in Beige and an Art Silk Jacquard Nehru Jacket in Pink</li><li> Do note: Footwear shown in the image is for presentation purposes only. Half to one inch may vary in measurement. (Slight variation in actual color vs. image is possible)</li></ul>USDtype_new:Kurta Pyjamacolorfam:Beige, Pinkfabric:Art SilkBeige, PinkArt SilkKurta Pyjama11%-20%MenReady to Ship, Within 2 days, Within 7 days, Within 10 days, Within 15 days, More than 15 DaysReadymadeWedding, FestiveMenswearButtons, Traditional34, 36, 38, 40, 4244, 46, 48, 50, 52