AW510K keyboard, backlight uniformity question

I recently purchased the AW510K keyboard. I noticed immediately that the alternate function characters like +, %, on the lower part of a given key are very dim compared to the main keyboard letters on the upper part of a key.  At times the alternate function characters  barely appear backlit. If one looks at the AWCC depiction of the backlit keyboard where one adjusts the colors the main characters and alternate function characters appear equally bright. I realize this is a graphical depiction and may not be accurate.

Looking under a single horizontal row of keys from the side on my keyboard it is apparent there are two strips of backlighting, and on my keyboard the upper strip is very bright, corresponding to the brightly illuminated upper part of the keys, whereas the lower strip is much dimmer corresponding to the dimly lit alternate characters.

I am wondering if other users notice this and the difference is by design? Or is a defect on my keyboard? If by design that is disappointing, as I have vision problems, and the low backlighting makes it hard for me to see the characters on the bottom half of the keys.

Greg