Adjusting Bed Temp values on Monoprice/Wanhao I3 (Repetier Firmware)
It is completely normal for the surface of the bed to be cooler than the indicated temperature. The thermistor goes on the underside of the bed, near the heating traces. The top of the bed (which is further away from the heating traces) will naturally be cooler.

It would be possible, though a lot of work, to build a custom thermistor table that more accurately reflects the surface of the bed, though that means your thermistor table will no longer reflect the characteristics of your thermistor, but instead reflect the particular circumstances under which you build your custom table (which would be affected by ambient temperature, any drafts, ...).

The accuracy of an infrared laser thermometer depends on the characteristics of the surface you're measuring for, so unless you adjusted the thermometer specifically to measure the aluminium surface of the bed, it's possible your thermometer is off as well.

The exact temperature of your bed doesn't matter anyways (you just need it approximately in the right ballpark) so I would suggest to just live with it. The 60C/90C figures are not supposed to be for the surface of the bed. They're meant to reflect the temperature reported by the printer. That said, 90C is a bit low for printing ABS (but the bed/power supply on your printer might not be powerful enough to get any higher).