Battery packs are rated in watt hours by multiplying voltage and amp-hours. Laptop batteries Ah rating is normally expressed in (mAh) milliamp hours (4.6Ah is equivalent to 4600mAH).
11.1V battery pack with 4.6Ah (4600mAh) will have (11.1 * 4.6) 51Wh capacity.
A battery pack mAH rating number defines how much charge the battery pack can hold, higher the mAh number, longer the run time. Also, higher or lower mAH ratings number compare to your existing battery pack will not cause any compatibility issues.
Battery packs are built by connecting individual cells in series and parallel. A battery voltage rating is calculated by multiplying number of cells in series with number 3.6V or 3.7V. For all practical purpose, there is no difference between individual cells rated at 3.6V or 3.7V. Some manufactures picked 3.6V while others used 3.7V for the same type of cell.
This explains that there is no difference between batteries rated at 10.8V and 11.1V, same is true for 14.4V and 14.8V battery packs.