Transformer - If the Output V number matches, does it matter that the A numbers are different"
"A numbers" and "V numbers" refer to the Ampere and Volt capacity of the unit, respectively.  Also, you don't have a "transformer".  What you have is a "power supply".  Transformers only put out AC, which is inherent to how they work.  The solid line above the dashed line is a symbol indicating DC, as apposed to AC.

So, your equipment came with a 5 Volt 1.8 Amp power supply, and you want to know whether you can replace the power supply with one rated for 5 Volts and 2.4 Amps.  Yes, you can.  The Volt ratings must match, but a higher Amp rating is OK.  This only indicates how much current the power supply is capable of delivering if the load demands it, not how much it will deliver.  Since 1.8 A is apparently sufficient for your device, the extra .6 A capacity of the new power supply won't be used but will do no harm.

This concept is like the limit on a credit card.  A $2,400 limit will still work even if you will only ever borrow $1,800.