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-art-silk-kurta-set-in-black-mse230338553Embroidered Art Silk Kurta Set in Blackhttps://medias.utsavfashion.com/media/catalog/product/cache/1/small_image/295x/040ec09b1e35df139433887a97daa66f/m/s/mse230.jpg100.8126USDInStock/men/men/plus/men/wedding/men/festive/men/art silk/men/black/men/kurta pyjama/men/resham/men/stone work/men/traditional/men/zariEmbroidered Art Silk Kurta Set in Black <ul><li> Detailed with resham, zari, cutdana and stone work</li><li> Available with an poly silk churidar in maroon</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 differ in measurement</li></ul>USDtype_new:Kurta Pyjamacolorfam:Blackfabric:Art SilkBlackArt SilkKurta Pyjama11%-20%MenWithin 15 days, More than 15 DaysReadymadeWedding, FestiveMenswearResham, Stone Work, Traditional, Zari38, 40, 4244, 46, 48, 50, 52, 54, 56, 58, 60