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-border-art-silk-dupatta-in-brown-mte5001575424Embroidered Border Art Silk Dupatta in Brownhttps://medias.utsavfashion.com/media/catalog/product/cache/1/small_image/295x/040ec09b1e35df139433887a97daa66f/e/m/embroidered-border-art-silk-dupatta-in-brown-v1-mte500.jpg37.647USDInStock/men/men/wedding/men/festive/men/art silk/men/brown/men/dupattas/men/mirror work/men/traditional/men/zariEmbroidered Border Art Silk Dupatta in Brown <ul><li> Art Silk Dupatta in Brown</li><li> Allured with Mirror Effect and Zari Work</li><li> Its Length and Width are 100 and 26 inches respectively</li><li> Do note: Kurta, Bottom and Footwear shown in the image is for presentation purposes only. (Slight variation in actual color vs. image is possible)</li></ul>USDadd-to-carttype_new:Dupattascolorfam:Brownfabric:Art SilkBrownArt SilkDupattas11%-20%MenReady to Ship, Within 2 days, Within 7 days, Within 10 days, Within 15 days, More than 15 DaysReadymadeWedding, FestiveMenswearMirror Work, Traditional, Zari