the idea is that you set up your goals so that you are losing whatever amount without factoring in exercise. so your maintenance calories less your deficit means you need to be eating at 1410-1760 cals. therefore, when you exercise, in order to maintain that loss deficit you have to eat back your exercise calories. otherwise the exercise calories become deficit calories. and while that might sound like a great thing [extra bonus deficit calories!] when you start having huge, regular shortfalls it can make loss harder. well, at least if you want to maintain your level of fitness and activity.
now, how many more you really need depends a lot on you and where you are. if you have 100+lbs to lose then eating back all of those calories becomes a little less important because you are large enough you can likely support a little larger deficit. which doesn't mean eat none of them back, but it's not as vital that you eat the rest back unless you're having a problem keeping up. but if you're fairly close to where you want to be 30lbs or so, you really do need to be eating those calories back. and basically all of them. your body doesn't have the excess reserves it needs to make up for larger deficits.
as far as the 1890 burn goes, where did you get that number from? snowshoeing is one of the higher calorie burning activities that i know of, and if you're doing it for any length of time 1890 doesn't sound unreasonable to me [though take this with a grain of salt, i'm a floridian and my knowledge of snow activities mostly lies in general theory and being happy far from them]. so check that burn number against other online sources that use your stats [unless you're wearing a heart rate monitor in which case use that info] to see if you were using some off info as the base. if you were using spark, make sure that your weight is updated so that it's using the most accurate info you can give it.
the final thing to factor in is frequency. if you're talking about doing this on a regular basis [weekly or more often], then it's really important you eat most of those calories back. say you do this 3 times a week. that's almost 6000 cals you're going to be burning. 7000 cals a week amounts to a 2lb loss per week. so that's almost 2lbs on top of what you already set your tracker to lose. which would be fine if you weighed 300-400lbs. but if you weigh under 200, that's the kind of deficit your body just doesn't have the reserves to make up. if you're snowshoeing once or twice a month it's fine to space out the extra calories over the month [about 130 per day] to make up the difference. even if you were doing it twice a week that would work as well, which is about an extra 500-600 cals a day.
-google first. ask questions later.