Zoom on writing on a <a href="https://en.wikipedia.org/wiki/Fluorescent_lamp" class="extiw" title="en:Fluorescent lamp">flurorescent tube</a>. The number 840 indicate that the IRC is in 80-90 and that the colour of the lamp correspond to 4000k (white)
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<span class="int-own-work" lang="en">Own work</span>