Low power mode not working

hi. We have 3 anchors and 1 tag. We are using the dwm-simple program. The tag is connected to the the PC and we log data by putty. We get a position for normal tag mode. When we are switching to low power mode we still get position every seconde. We expect to have no output on UART until we move the tag. What are we doing wrong? For what does time=0 stand for?
Following is the output in low power mode:

nmg
mode: tn (act,twr,lp,le)
dwm>
T:0 POS:[2249,1972,265,86] DIST0:0x2E8C[3364,841,0]=[1606,100] DIST1:0x2D02[0,1682,0]=[2262,100] DIST2:0x0D00[0,0,0]=[3101,100]
x=2249, y=1972, z=265, qf=86
time=0

regards,
thomas