Variation in color values from input to output

[RedFlyer]

Using the command: convert -size 850x850 canvas:'rgb(255,0,0)' testBox.jpg

I was able to create a lovely red box, but when I take it into photoshop and check the value of the red it reads as 254,0,0. When I try it with green I get 0,255,1 and with blue it's 0,0,254.

I also tried adding a profile to see if that would help: convert -size 850x850 -profile /AdobeRGB1998.icc canvas:'rgb(0,0,255)' testBox.jpg
But it produced the same results. Did the same with sRGB, with more of the same.

Anyone have any thoughts on what's causing the variance from the input to output, and know what I could do to fix it?

Thank you so much for any replies, and hope you have a great day!

[snibgo]

Jpeg is lossy compression, which means it changes color values.

If you want to keep the specified values, don't use lossy compression.

[RedFlyer]

Gotcha, thanks!