When I get Sertag electronic shelf labels, why did this battery appear to be 90 percent?

When I get Sertag electronic shelf labels, why did this battery appear to be 90 percent?

When I get Sertag electronic shelf labels, why did this battery appear to be 90 percent?
The percentage of electronic shelf label battery is based on the tag voltage, which is an interval. 90% does not mean that the battery has been used, and the voltage may be just at the critical value. Please refer to the figure
electronic shelf labels
electronic price tags