My body math index

Here is an actual thing that happened yesterday at LabCorp, where I went for a routine biometric screening for health insurance purposes.

Tech: How tall are you?

Me: Five-eleven.

Tech takes out phone, taps a while at the screen, writes a number on the form, then goes out of room. Me looks at the form. Me's height is written as 61.3. Tech returns to room.

Me: Is that supposed to be in inches?

Tech: What?

Me: My height.

Tech: It is.

Me: Five-eleven is 71 inches.

Tech: No, it's not.

Me: Yes, it is. Five times twelve is 60, plus eleven is 71.

Tech. Oh. [pause] I timesed by eleven.

Me drives self crazy trying to figure out how multiplying any reasonable operand by eleven yields 61.3, must be restrained.

Update:  A Facebook friend points out that 5.11 x 12 = 61.32. Mystery ... solved?