26800 blue light blinking while charging other device

hey guys. i have the 26800 battery with the 4 led lights.
im now emptying it and then ill fully charge it.
from the box it had about 50%. (2 lights)
after 10 mins one light went off, so i assumed it actually had about 25% of the box.
it charged my phone nicely and the blue led was solid blue.
few minutes ago it started to blink blue.
what does that mean? (its still charging my phone, but it blinks)
*if it means its low on battery its a shame, cuz it charged only about 2 hours-few phones- each of them had 60%+ battery (so it charged about only 2,500mha worth of battery…:anguished:
is possible its already low on battery?!?!