Alyc: on an "western" equipment such as this 737, the most robust way to operate in height-metric-QFE scenarios is to convert them to altitude-feet-QNH.
Some western operators require their crews to confirm the QNH from ATC, whilst calculated.
Once you learn how to do it, it is very good procedure. The conversion tables are provided on an approach chart.
vlky: My understanding is that FR24 shows ADS-B data from XPDR, that being QNE based altitude. With QNH = 988 the difference from FR24 readout to cockpit indicated altitude is 700 ft. Hence 950 ft on FR24 = 250 on ALT = ground.