When comparing the current ratings on your fan label to the fan rating that is noted in the data sheet you will notice a discrepancy with most fans. The current rating on the data sheet will be the nominal or average current draw for the fan. This is typically while the fan is in free air. The current (amperage) rating that is marked on the label is required by UL to be the worst case maximum current rating that the fan will draw.
For this example we will look at NMB part 2410SB-04W-B49-B50. This fan has a current rating of .1A in the data sheet. Below I have attached a picture of the actual fan. As you can see the rating on the fan is .14A. If you were to look closely at the data sheet you would see a note for the current that states *Average Values in Free Air. There is no information specifically linking the value on the label to the individual fan.